v0.6.0

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -62,6 +62,22 @@ $ pip install pytheory
 ['C major', 'G major', 'A minor', 'F major']
 ```
 
+## Keys and Progressions
+
+```pycon
+>>> from pytheory import Key
+
+>>> key = Key("G", "major")
+>>> key.chords
+['G major', 'A minor', 'B minor', 'C major', 'D major', 'E minor', 'F# diminished']
+
+>>> [c.identify() for c in key.progression("I", "V", "vi", "IV")]
+['G major', 'D major', 'E minor', 'C major']
+
+>>> Key.detect("C", "E", "G", "A", "D")
+<Key C major>
+```
+
 ## Chord Analysis
 
 ```pycon
@@ -116,7 +132,10 @@ $ pip install pytheory
 >>> Fretboard.keyboard(25, "C3")      # 25-key MIDI controller
 
 >>> CHARTS['western']['Am'].fingering(fretboard=Fretboard.guitar())
-(0, 1, 2, 2, 0, 0)
+Fingering(e=0, B=1, G=2, D=2, A=0, E=0)
+
+>>> Fretboard.guitar().fingering(0, 1, 0, 2, 3, 0).identify()
+'C major'
 ```
 
 ## Audio Playback

docs/guide/chords.rst

@@ -127,13 +127,33 @@ Quality       Intervals         Example tones (from C)
    >>> chart["Cm7"].acceptable_tone_names
    ('C', 'D#', 'G', 'A#')    # Eb and Bb shown as sharps
 
-Building Chords Manually
--------------------------
+Building Chords
+---------------
+
+Several convenience constructors make chord creation concise:
 
 .. code-block:: python
 
-   from pytheory import Tone, Chord
+   from pytheory import Chord
 
+   # From note names (simplest)
+   Chord.from_tones("C", "E", "G")           # <Chord C major>
+   Chord.from_tones("A", "C", "E")           # <Chord A minor>
+
+   # From a chord name (uses the built-in chart)
+   Chord.from_name("Am7")                    # <Chord A minor 7th>
+   Chord.from_name("G7")                     # <Chord G dominant 7th>
+
+   # From root + semitone intervals
+   Chord.from_intervals("C", 4, 7)           # <Chord C major>
+   Chord.from_intervals("D", 3, 7)           # <Chord D minor>
+   Chord.from_intervals("G", 4, 7, 10)       # <Chord G dominant 7th>
+
+   # From MIDI note numbers
+   Chord.from_midi_message(60, 64, 67)       # <Chord C major>
+
+   # Full manual construction
+   from pytheory import Tone
    c_major = Chord(tones=[
        Tone.from_string("C4", system="western"),
        Tone.from_string("E4", system="western"),

docs/guide/fretboard.rst

@@ -179,9 +179,22 @@ on any instrument. It scores each possibility by:
    fb = Fretboard.guitar()
    c = CHARTS["western"]["C"]
 
-   # Best single fingering
-   print(c.fingering(fretboard=fb))
-   # (0, 1, 0, 2, 3, 0)
+   # Fingerings return a Fingering object with labeled strings
+   f = c.fingering(fretboard=fb)
+   print(f)
+   # Fingering(e=0, B=1, G=0, D=2, A=3, E=0)
+
+   # Access by string name or index
+   f['A']     # 3
+   f[1]       # 1 (B string)
+
+   # Identify the chord directly from a fingering
+   f.identify()   # 'C major'
+
+   # Convert to a Chord for further analysis
+   chord = f.to_chord()
+   chord.harmony       # consonance score
+   chord.intervals     # [4, 3] — major triad
 
    # All equally-scored fingerings
    all_c = c.fingering(fretboard=fb, multiple=True)
@@ -190,11 +203,22 @@ on any instrument. It scores each possibility by:
    f = CHARTS["western"]["F"]
    print(f.fingering(fretboard=fb))
 
+You can also go from fret positions to chord identification:
+
+.. code-block:: python
+
+   # "What chord am I playing?"
+   fb = Fretboard.guitar()
+   f = fb.fingering(0, 0, 0, 2, 2, 0)
+   print(f)            # Fingering(e=0, B=0, G=0, D=2, A=2, E=0)
+   print(f.identify()) # E minor
+
 Reading Fingerings
 ~~~~~~~~~~~~~~~~~~
 
-The tuple ``(0, 1, 0, 2, 3, 0)`` reads from the highest string to the
-lowest::
+Each position is labeled with its string name. Duplicate string names
+are disambiguated — on a standard guitar, high E appears as ``e`` and
+low E as ``E``::
 
     e|--0--    (open — E)
     B|--1--    (fret 1 — C)
@@ -205,6 +229,22 @@ lowest::
 
 A value of ``None`` means the string is muted (not played).
 
+ASCII Tablature
+~~~~~~~~~~~~~~~
+
+For a more visual representation, use ``tab()``:
+
+.. code-block:: python
+
+   >>> print(CHARTS["western"]["C"].tab(fretboard=fb))
+   C
+   E|--0--
+   B|--1--
+   G|--0--
+   D|--2--
+   A|--3--
+   E|--0--
+
 Generating Full Charts
 ----------------------
 

docs/guide/playback.rst

@@ -25,14 +25,13 @@ Playing a Chord
 
 .. code-block:: python
 
-   from pytheory import Chord, Tone, play
+   from pytheory import Chord, play
 
-   c_major = Chord(tones=[
-       Tone.from_string("C4", system="western"),
-       Tone.from_string("E4", system="western"),
-       Tone.from_string("G4", system="western"),
-   ])
-   play(c_major, t=2_000)  # Play for 2 seconds
+   # From a chord name
+   play(Chord.from_name("Am7"), t=2_000)
+
+   # From note names
+   play(Chord.from_tones("C", "E", "G"), t=2_000)
 
 Waveform Types
 --------------

docs/guide/quickstart.rst

@@ -40,10 +40,14 @@ Create tones, build scales, and explore music theory:
    IV = c_major.triad(3)   # F A C  (F major)
    V  = c_major.triad(4)   # G B D  (G major)
 
-   # Guitar chord fingerings
+   # Guitar chord fingerings — labeled with string names
    fb = Fretboard.guitar()
    fingering = CHARTS["western"]["Am"].fingering(fretboard=fb)
-   print(fingering)  # (0, 1, 2, 2, 0, 0)
+   print(fingering)  # Fingering(e=0, B=1, G=2, D=2, A=0, E=0)
+
+   # Identify a chord from fret positions
+   f = fb.fingering(0, 1, 0, 2, 3, 0)
+   print(f.identify())  # C major
 
 What's Included
 ---------------
@@ -54,9 +58,12 @@ What's Included
   10 maqamat, 6 Japanese pentatonic scales, blues, pentatonic,
   slendro, pelog, and more
 - **Pitch calculation** in equal, Pythagorean, and meantone temperaments
+- **Chord identification**: name any chord from its notes, intervals, or
+  MIDI numbers (17 chord types recognized)
 - **Chord charts** with 144 pre-built chords (12 roots x 12 qualities)
 - **Chord analysis**: consonance scoring, Plomp-Levelt dissonance,
-  beat frequency calculation
-- **Fingering generation** for guitar (8 tunings), bass, ukulele, or
-  any custom fretted instrument
+  beat frequency calculation, harmonic tension, voice leading
+- **Key detection** and **Roman numeral analysis** (I-IV-V-I progressions)
+- **Fingering generation** for 25 instruments with labeled string names,
+  including guitar (8 tunings), bass, ukulele, mandolin, and more
 - **Audio playback** with sine, sawtooth, and triangle wave synthesis

docs/guide/scales.rst

@@ -215,6 +215,35 @@ Some of the most-used chord progressions in Western music:
   My Heart Will Go On)
 - **I–IV–vi–V** — axis of awesome (many, many pop songs)
 
+The :class:`~pytheory.scales.Key` class makes working with progressions
+easy:
+
+.. code-block:: python
+
+   from pytheory import Key
+
+   key = Key("G", "major")
+
+   # Build a progression from Roman numerals
+   chords = key.progression("I", "V", "vi", "IV")
+   for c in chords:
+       print(c.identify())
+   # G major, D major, E minor, C major
+
+   # Nashville number system (same thing, with integers)
+   key.nashville(1, 5, 6, 4)
+
+   # All diatonic triads in the key
+   key.chords
+   # ['G major', 'A minor', 'B minor', 'C major', ...]
+
+   # All diatonic seventh chords
+   key.seventh_chords
+   # ['G major 7th', 'A minor 7th', ...]
+
+   # Detect the key from a set of notes
+   Key.detect("C", "E", "G", "A", "D")   # <Key C major>
+
 The 12-Bar Blues
 ~~~~~~~~~~~~~~~~
 

docs/guide/tones.rst

@@ -125,9 +125,47 @@ same note name:
    >>> c5.pitch(temperament="pythagorean")
    521.48   # Slightly different!
 
-   # Symbolic output (SymPy expression)
+Symbolic Pitch
+~~~~~~~~~~~~~~
+
+Pass ``symbolic=True`` to get exact pitch ratios as
+`SymPy <https://en.wikipedia.org/wiki/SymPy>`_ expressions instead of
+floating-point approximations. This is useful for mathematical analysis,
+proving tuning relationships, or comparing temperaments with exact
+arithmetic.
+
+.. code-block:: python
+
+   >>> a4 = Tone.from_string("A4", system="western")
+
+   # Equal temperament: irrational ratios (roots of 2)
    >>> a4.pitch(symbolic=True)
    440
+   >>> Tone.from_string("C5", system="western").pitch(symbolic=True)
+   440*2**(1/4)
+
+   # Pythagorean: pure rational ratios (powers of 3/2)
+   >>> Tone.from_string("G4", system="western").pitch(
+   ...     temperament="pythagorean", symbolic=True)
+   660
+
+   # Compare the major third across temperaments
+   >>> e4 = Tone.from_string("E4", system="western")
+   >>> e4.pitch(temperament="equal", symbolic=True)
+   440*2**(1/3)
+   >>> e4.pitch(temperament="pythagorean", symbolic=True)
+   12160/27
+   >>> e4.pitch(temperament="meantone", symbolic=True)
+   550
+
+   # Symbolic expressions can be evaluated to any precision
+   >>> e4.pitch(symbolic=True).evalf(50)
+   329.62755691286991583007431157433859631791591649985
+
+The symbolic output reveals *why* temperaments differ: equal temperament
+uses irrational numbers (roots of 2), Pythagorean uses powers of 3/2
+(rational but accumulating error), and meantone tunes thirds to the
+pure 5/4 ratio (sacrificing fifths).
 
 Intervals and Arithmetic
 -------------------------
@@ -248,12 +286,19 @@ D major scale is D E F# G A B C# — not D E Gb G A B Db, even though
 F#=Gb and C#=Db.
 
 PyTheory uses sharps by default (following the tone list ordering), but
-tones carry their enharmonic equivalents:
+every tone knows its enharmonic spelling:
 
 .. code-block:: python
 
-   >>> Tone.from_tuple(("C#", "Db")).names()
-   ['C#', 'Db']
+   >>> Tone.from_string("C#4", system="western").enharmonic
+   'Db'
+
+   >>> Tone.from_string("A#4", system="western").enharmonic
+   'Bb'
+
+   # Natural notes have no enharmonic
+   >>> Tone.from_string("C4", system="western").enharmonic is None
+   True
 
 The Circle of Fifths
 --------------------
@@ -265,11 +310,15 @@ to the starting note:
 
 .. code-block:: python
 
-   >>> t = Tone.from_string("C4", system="western")
-   >>> for i in range(12):
-   ...     print(t.name, end=" ")
-   ...     t = t + 7
-   C G D A E B F# C# G# D# A# F
+   >>> c4 = Tone.from_string("C4", system="western")
+
+   # Clockwise — ascending fifths (adds sharps)
+   >>> [t.name for t in c4.circle_of_fifths()]
+   ['C', 'G', 'D', 'A', 'E', 'B', 'F#', 'C#', 'G#', 'D#', 'A#', 'F']
+
+   # Counter-clockwise — ascending fourths (adds flats)
+   >>> [t.name for t in c4.circle_of_fourths()]
+   ['C', 'F', 'A#', 'D#', 'G#', 'C#', 'F#', 'B', 'E', 'A', 'D', 'G']
 
 Each step clockwise adds one sharp to the key signature; each step
 counter-clockwise (ascending by fourths = 5 semitones) adds one flat.

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "pytheory"
-version = "0.4.1"
+version = "0.6.0"
 description = "Music Theory for Humans"
 readme = "README.md"
 license = "MIT"

pytheory/__init__.py

@@ -1,12 +1,12 @@
 """PyTheory: Music Theory for Humans."""
 
-__version__ = "0.4.1"
+__version__ = "0.6.0"
 
 from .tones import Tone, Interval
 from .systems import System, SYSTEMS
 from .scales import Scale, TonedScale, Key, PROGRESSIONS
 from .chords import Chord, Fretboard, analyze_progression
-from .charts import CHARTS, charts_for_fretboard
+from .charts import CHARTS, Fingering, charts_for_fretboard
 
 try:
     from .play import play, Synth
@@ -19,7 +19,7 @@ Note = Tone
 
 __all__ = [
     "Tone", "Note", "Interval", "Scale", "TonedScale", "Key",
-    "PROGRESSIONS", "Chord", "Fretboard", "analyze_progression",
+    "PROGRESSIONS", "Chord", "Fretboard", "Fingering", "analyze_progression",
     "System", "SYSTEMS", "CHARTS", "charts_for_fretboard",
     "play", "Synth",
 ]

pytheory/charts.py

@@ -1,4 +1,5 @@
 import itertools
+from typing import Optional
 
 from .systems import SYSTEMS
 from .tones import Tone
@@ -6,6 +7,106 @@ from .tones import Tone
 QUALITIES = ("", "maj", "m", "5", "7", "9", "dim", "m6", "m7", "m9", "maj7", "maj9")
 MAX_FRET = 7
 
+
+class Fingering:
+    """A chord fingering labeled with string names.
+
+    Provides both index and named access to fret positions, making it
+    clear which string each position corresponds to.
+
+    Example::
+
+        >>> f = Fingering(positions=(0, 3, 2, 0, 1, 0),
+        ...               string_names=('E', 'A', 'D', 'G', 'B', 'e'))
+        >>> f
+        Fingering(E=0, A=3, D=2, G=0, B=1, e=0)
+        >>> f['A']
+        3
+        >>> f[1]
+        3
+    """
+
+    def __init__(self, positions: tuple, string_names: tuple[str, ...], *, fretboard=None) -> None:
+        self.positions = tuple(positions)
+        self._fretboard = fretboard
+        # Disambiguate duplicate names: for standard guitar tuning
+        # (high-to-low), the first occurrence of a duplicate becomes
+        # lowercase (e.g. high E → 'e') while the last keeps uppercase.
+        from collections import Counter
+        name_counts = Counter(string_names)
+        seen: dict[str, int] = {}
+        unique_names: list[str] = []
+        for name in string_names:
+            seen[name] = seen.get(name, 0) + 1
+            if name_counts[name] > 1 and seen[name] < name_counts[name]:
+                unique_names.append(name.lower())
+            else:
+                unique_names.append(name)
+
+        self.string_names = tuple(unique_names)
+        self._map = dict(zip(self.string_names, self.positions))
+
+    def __repr__(self) -> str:
+        pairs = ", ".join(
+            f"{name}={'x' if pos is None else pos}"
+            for name, pos in zip(self.string_names, self.positions)
+        )
+        return f"Fingering({pairs})"
+
+    def __getitem__(self, key):
+        if isinstance(key, int):
+            return self.positions[key]
+        return self._map[key]
+
+    def __iter__(self):
+        return iter(self.positions)
+
+    def __len__(self):
+        return len(self.positions)
+
+    def __eq__(self, other):
+        if isinstance(other, Fingering):
+            return self.positions == other.positions and self.string_names == other.string_names
+        if isinstance(other, tuple):
+            return self.positions == other
+        return NotImplemented
+
+    @property
+    def tones(self):
+        """Return the sounding tones for this fingering.
+
+        Requires that the Fingering was created with a fretboard reference.
+        Muted strings (``None``) are excluded.
+        """
+        if self._fretboard is None:
+            raise ValueError("Cannot resolve tones without a fretboard reference.")
+        tones = []
+        for pos, tone in zip(self.positions, self._fretboard.tones):
+            if pos is not None:
+                tones.append(tone.add(pos))
+        return tones
+
+    def to_chord(self, fretboard=None) -> "Chord":
+        """Apply this fingering to a fretboard, returning a Chord.
+
+        Strings with ``None`` positions (muted) are excluded.
+        If no fretboard is given, uses the one stored at creation time.
+        """
+        from .chords import Chord
+
+        fb = fretboard or self._fretboard
+        if fb is None:
+            raise ValueError("No fretboard provided.")
+        tones = []
+        for pos, tone in zip(self.positions, fb.tones):
+            if pos is not None:
+                tones.append(tone.add(pos))
+        return Chord(tones=tones)
+
+    def identify(self) -> Optional[str]:
+        """Identify the chord name from this fingering."""
+        return self.to_chord().identify()
+
 CHARTS = {}
 CHARTS["western"] = []
 
@@ -148,11 +249,12 @@ class NamedChord:
                 if fingering_score(possible_fingering) == max_score:
                     yield possible_fingering
 
+        string_names = tuple(t.name for t in fretboard.tones)
         best_fingerings = tuple([g for g in gen()])
         if not multiple:
-            return self.fix_fingering(best_fingerings[0])
+            return Fingering(self.fix_fingering(best_fingerings[0]), string_names, fretboard=fretboard)
         else:
-            return tuple([self.fix_fingering(f) for f in best_fingerings])
+            return tuple([Fingering(self.fix_fingering(f), string_names, fretboard=fretboard) for f in best_fingerings])
 
     def tab(self, *, fretboard):
         """Render this chord as ASCII guitar tablature.

pytheory/chords.py

@@ -680,8 +680,8 @@ class Chord:
         """
         return Chord(tones=[t for t in self.tones if t.name != tone_name])
 
-    def fingering(self, *positions: int) -> Chord:
-        """Apply fret positions to each tone, returning a new Chord.
+    def fingering(self, *positions: int) -> "Fingering":
+        """Apply fret positions to each tone, returning a Fingering.
 
         Each position value is added (in semitones) to the corresponding
         tone. The number of positions must match the number of tones.
@@ -690,22 +690,21 @@ class Chord:
             *positions: One integer per tone indicating the fret offset.
 
         Returns:
-            A new :class:`Chord` with each tone shifted by its position.
+            A :class:`Fingering` labeled with tone names.
 
         Raises:
             ValueError: If the number of positions doesn't match the
                 number of tones.
         """
+        from .charts import Fingering
+
         if not len(positions) == len(self.tones):
             raise ValueError(
                 "The number of positions must match the number of tones (strings)."
             )
 
-        tones = []
-        for i, tone in enumerate(self.tones):
-            tones.append(tone.add(positions[i]))
-
-        return Chord(tones=tones)
+        string_names = tuple(t.name for t in self.tones)
+        return Fingering(positions, string_names)
 
 
 class Fretboard:
@@ -1252,8 +1251,8 @@ class Fretboard:
 
         return "\n".join(lines)
 
-    def fingering(self, *positions: int) -> Chord:
-        """Apply fret positions to each string, returning a Chord.
+    def fingering(self, *positions: int) -> "Fingering":
+        """Apply fret positions to each string, returning a Fingering.
 
         Each position value is added (in semitones) to the corresponding
         open-string tone. The number of positions must match the number
@@ -1263,22 +1262,22 @@ class Fretboard:
             *positions: One integer per string indicating the fret number.
 
         Returns:
-            A :class:`Chord` with each tone shifted by its fret position.
+            A :class:`Fingering` labeled with string names. Call
+            ``.to_chord(fretboard)`` or use the resulting chord directly.
 
         Raises:
             ValueError: If the number of positions doesn't match the
                 number of strings.
         """
+        from .charts import Fingering
+
         if not len(positions) == len(self.tones):
             raise ValueError(
                 "The number of positions must match the number of tones (strings)."
             )
 
-        tones = []
-        for i, tone in enumerate(self.tones):
-            tones.append(tone.add(positions[i]))
-
-        return Chord(tones=tones)
+        string_names = tuple(t.name for t in self.tones)
+        return Fingering(positions, string_names, fretboard=self)
 
 
 def analyze_progression(chords: list[Chord], key: str = "C", mode: str = "major") -> list[str | None]:

pytheory/cli.py

@@ -91,6 +91,42 @@ def cmd_progression(args):
         print(f"    {numeral:6s}  {chord}")
 
 
+def cmd_play(args):
+    from .tones import Tone
+    from .chords import Chord
+    from .play import play, Synth
+
+    synth_map = {"sine": Synth.SINE, "saw": Synth.SAW, "triangle": Synth.TRIANGLE}
+    synth = synth_map[args.synth]
+    duration = args.duration
+
+    # Try chord name first (e.g. "Am", "Cmaj7"), then fall back to individual notes.
+    if len(args.notes) == 1:
+        note = args.notes[0]
+        # Try as chord name first (Am, G7, Cmaj7, etc.)
+        try:
+            target = Chord.from_name(note)
+            name = target.identify() or note
+            label = f"{name} ({' '.join(t.full_name for t in target.tones)})"
+        except (ValueError, KeyError):
+            # Fall back to single tone
+            target = Tone.from_string(
+                note if any(c.isdigit() for c in note) else f"{note}4",
+                system="western")
+            label = target.full_name
+    else:
+        tones = [Tone.from_string(n if any(c.isdigit() for c in n) else f"{n}4",
+                                  system="western") for n in args.notes]
+        target = Chord(tones=tones)
+        name = target.identify() or "Custom"
+        label = f"{name} ({' '.join(t.full_name for t in tones)})"
+
+    print(f"  Playing: {label}")
+    print(f"  Synth:   {args.synth}")
+    print(f"  Duration: {duration} ms")
+    play(target, temperament=args.temperament, synth=synth, t=duration)
+
+
 def cmd_detect(args):
     from .scales import Key
     key = Key.detect(*args.notes)
@@ -141,6 +177,18 @@ def main():
     p.add_argument("mode", help="Mode (e.g. major, minor)")
     p.add_argument("numerals", nargs="+", help="Roman numerals (e.g. I V vi IV)")
 
+    # play
+    p = sub.add_parser("play", help="Play notes or chords (e.g. pytheory play C E G)")
+    p.add_argument("notes", nargs="+", help="Note names, with optional octave (e.g. C4, A#3, or just C E G)")
+    p.add_argument("--synth", "-s", default="sine",
+                   choices=["sine", "saw", "triangle"],
+                   help="Waveform (default: sine)")
+    p.add_argument("--duration", "-d", type=int, default=1000,
+                   help="Duration in milliseconds (default: 1000)")
+    p.add_argument("--temperament", "-t", default="equal",
+                   choices=["equal", "pythagorean", "meantone"],
+                   help="Tuning temperament (default: equal)")
+
     # detect
     p = sub.add_parser("detect", help="Detect key from notes (e.g. pytheory detect C E G)")
     p.add_argument("notes", nargs="+", help="Note names")
@@ -157,6 +205,7 @@ def main():
         "key": cmd_key,
         "fingering": cmd_fingering,
         "progression": cmd_progression,
+        "play": cmd_play,
         "detect": cmd_detect,
     }
     commands[args.command](args)

pytheory/systems.py

@@ -24,6 +24,16 @@ class System:
         from . import Tone
         return tuple([Tone.from_tuple(tone) for tone in self.tone_names])
 
+    def resolve_name(self, name: str) -> str | None:
+        """Resolve a note name (including flats) to the canonical name.
+
+        Returns the primary name if found, or None if not recognized.
+        """
+        for names in self.tone_names:
+            if name in names:
+                return names[0]
+        return None
+
 
     @property
     def scales(self):

pytheory/tones.py

@@ -71,7 +71,7 @@ class Tone:
     @property
     def exists(self) -> bool:
         """True if this tone's name is found in the associated system."""
-        return self.name in self.system.tones
+        return self.system.resolve_name(self.name) is not None
 
     @property
     def system(self) -> object:
@@ -331,11 +331,17 @@ class Tone:
     def _index(self) -> int:
         """The index of this tone within its associated system's tone list.
 
+        Resolves enharmonic names (e.g. 'Db' → 'C#') before lookup.
+
         Raises:
-            ValueError: If no system is associated with this tone.
+            ValueError: If no system is associated with this tone or
+                the name is not found.
         """
         try:
-            return self.system.tones.index(self.name)
+            canonical = self.system.resolve_name(self.name)
+            if canonical is None:
+                raise ValueError(f"Tone {self.name!r} not found in system")
+            return self.system.tones.index(canonical)
         except AttributeError:
             raise ValueError("Tone index cannot be referenced without a system!")
 

test_pytheory.py

@@ -2622,7 +2622,7 @@ def test_tension_empty():
 
 def test_version():
     import pytheory
-    assert pytheory.__version__ == "0.4.1"
+    assert pytheory.__version__ == "0.6.0"
 
 
 def test_all_exports():
@@ -3647,3 +3647,80 @@ def test_charts_muted_string():
     nc = NamedChord(tone_name="C", quality="")
     fixed = nc.fix_fingering((0, -1, 2))
     assert fixed == (0, None, 2)
+
+
+# ── Flat note support ─────────────────────────────────────────────────────────
+
+def test_flat_tone_from_string():
+    db = Tone.from_string("Db4", system="western")
+    assert db.name == "Db"
+    assert db.octave == 4
+
+
+def test_flat_tone_frequency_matches_sharp():
+    db = Tone.from_string("Db4", system="western")
+    cs = Tone.from_string("C#4", system="western")
+    assert db.frequency == cs.frequency
+
+
+def test_flat_tone_frequency_all_enharmonics():
+    pairs = [("Bb3", "A#3"), ("Eb4", "D#4"), ("Gb4", "F#4"), ("Ab4", "G#4")]
+    for flat, sharp in pairs:
+        f = Tone.from_string(flat, system="western").frequency
+        s = Tone.from_string(sharp, system="western").frequency
+        assert f == s, f"{flat} != {sharp}"
+
+
+def test_flat_tone_arithmetic():
+    db = Tone.from_string("Db4", system="western")
+    result = db + 2
+    assert result.name == "D#"
+    assert result.octave == 4
+
+
+def test_flat_tone_interval():
+    c4 = Tone.from_string("C4", system="western")
+    db4 = Tone.from_string("Db4", system="western")
+    assert db4 - c4 == 1
+
+
+def test_flat_tone_exists():
+    db = Tone.from_string("Db4", system="western")
+    assert db.exists is True
+
+
+def test_flat_tone_index_resolves():
+    db = Tone.from_string("Db4", system="western")
+    cs = Tone.from_string("C#4", system="western")
+    assert db._index == cs._index
+
+
+def test_flat_chord_from_tones():
+    chord = Chord.from_tones("Db", "F", "Ab")
+    assert chord.identify() == "Db major"
+
+
+def test_flat_chord_from_tones_minor():
+    chord = Chord.from_tones("Bb", "Db", "F")
+    assert chord.identify() == "Bb minor"
+
+
+def test_flat_chord_from_tones_seventh():
+    chord = Chord.from_tones("Eb", "G", "Bb", "Db")
+    assert chord.identify() == "Eb dominant 7th"
+
+
+def test_system_resolve_name_sharp():
+    assert SYSTEMS["western"].resolve_name("C#") == "C#"
+
+
+def test_system_resolve_name_flat():
+    assert SYSTEMS["western"].resolve_name("Db") == "C#"
+
+
+def test_system_resolve_name_natural():
+    assert SYSTEMS["western"].resolve_name("C") == "C"
+
+
+def test_system_resolve_name_unknown():
+    assert SYSTEMS["western"].resolve_name("X") is None