Add analog oscillator drift for synth warmth

Per-note random pitch wobble (gaussian, ±cents scaled by analog param)
simulates analog oscillator instability. Applied to synth_lead (0.3),
synth_pad (0.4), synth_bass (0.2), acid_bass (0.3), electric_piano
(0.2), organ (0.15). Subtle enough to add life without sounding
out of tune.

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

pytheory/play.py

@@ -2660,7 +2660,7 @@ def _render_notes_to_buf(notes, buf, samples_per_beat, total_samples,
                          filter_sustain=0.0, filter_amount=0.0,
                          vel_to_filter=0.0, filter_q=0.707,
                          synth_kwargs=None, temperament="equal",
-                         reference_pitch=440.0):
+                         reference_pitch=440.0, analog=0.0):
     """Render a list of Notes into an existing buffer at the correct positions."""
     import random as _rnd
 
@@ -2692,6 +2692,12 @@ def _render_notes_to_buf(notes, buf, samples_per_beat, total_samples,
                     pitches = [t.pitch(temperament=temperament, reference_pitch=reference_pitch) for t in note.tone.tones]
                 else:
                     pitches = [note.tone.pitch(temperament=temperament, reference_pitch=reference_pitch)]
+                # Analog drift: slight random pitch offset per note,
+                # simulating analog oscillator instability. Each note
+                # gets a unique drift amount (±cents scaled by analog).
+                if analog > 0:
+                    pitches = [hz * (2 ** (_rnd.gauss(0, analog * 5) / 1200))
+                               for hz in pitches]
                 # Render oscillators (pass synth_kwargs for FM etc.)
                 waves = [synth_fn(hz, n_samples=n_samples, **_skw)
                          for hz in pitches]
@@ -2956,7 +2962,8 @@ def render_score(score):
                     filter_q=part.lowpass_q,
                     synth_kwargs=synth_kwargs,
                     temperament=_temperament,
-                    reference_pitch=_ref_pitch)
+                    reference_pitch=_ref_pitch,
+                    analog=part.analog)
 
             # Apply effects — segmented if automation exists
             auto_points = part._get_automation_points()

pytheory/rhythm.py

@@ -26,12 +26,14 @@ INSTRUMENTS = {
         "detune": 6, "chorus": 0.2, "chorus_rate": 1.0,
         "lowpass": 4000, "saturation": 0.15,
         "tremolo_depth": 0.15, "tremolo_rate": 4.5,
+        "analog": 0.2,
     },
     "organ": {
         "synth": "organ_synth", "envelope": "organ",
         "chorus": 0.2, "chorus_rate": 5.5,
         "lowpass": 5000,
         "phaser": 0.15, "phaser_rate": 0.4,
+        "analog": 0.15,
     },
     "harpsichord": {
         "synth": "pluck_synth", "envelope": "none",
@@ -227,6 +229,7 @@ INSTRUMENTS = {
         "delay": 0.2, "delay_time": 0.25, "delay_feedback": 0.3,
         "filter_attack": 0.01, "filter_decay": 0.3,
         "filter_sustain": 0.2, "filter_amount": 3000,
+        "analog": 0.3,
     },
     "synth_pad": {
         "synth": "supersaw", "envelope": "pad",
@@ -234,6 +237,7 @@ INSTRUMENTS = {
         "chorus": 0.2,
         "phaser": 0.3, "phaser_rate": 0.3,
         "sub_osc": 0.2,
+        "analog": 0.4,
     },
     "synth_bass": {
         "synth": "saw", "envelope": "pluck",
@@ -241,6 +245,7 @@ INSTRUMENTS = {
         "filter_attack": 0.005, "filter_decay": 0.2,
         "filter_sustain": 0.0, "filter_amount": 2000,
         "sub_osc": 0.4,
+        "analog": 0.2,
     },
     "acid_bass": {
         "synth": "saw", "envelope": "pad",
@@ -250,6 +255,7 @@ INSTRUMENTS = {
         "filter_attack": 0.005, "filter_decay": 0.15,
         "filter_sustain": 0.0, "filter_amount": 4000,
         "vel_to_filter": 3000,
+        "analog": 0.3,
     },
     "808_bass": {
         "synth": "sine", "envelope": "pluck",
@@ -2006,6 +2012,7 @@ class Part:
                  phaser_rate: float = 0.5,
                  cabinet: float = 0.0,
                  cabinet_brightness: float = 0.5,
+                 analog: float = 0.0,
                  fm_ratio: float = 2.0,
                  fm_index: float = 3.0):
         self.name = name
@@ -2051,6 +2058,7 @@ class Part:
         self.phaser_rate = phaser_rate
         self.cabinet = cabinet
         self.cabinet_brightness = cabinet_brightness
+        self.analog = analog
         self.fm_ratio = fm_ratio
         self.fm_index = fm_index
         self._system = "western"  # default, overridden by Score.part()
@@ -2648,6 +2656,7 @@ class Score:
              phaser_rate: float = None,
              cabinet: float = None,
              cabinet_brightness: float = None,
+             analog: float = None,
              fm_ratio: float = None,
              fm_index: float = None,
              fretboard=None) -> Part:
@@ -2760,6 +2769,7 @@ class Score:
             "tremolo_depth": tremolo_depth, "tremolo_rate": tremolo_rate,
             "phaser": phaser, "phaser_rate": phaser_rate,
             "cabinet": cabinet, "cabinet_brightness": cabinet_brightness,
+            "analog": analog,
             "fm_ratio": fm_ratio, "fm_index": fm_index,
         }
         for k, v in _locals.items():