Add software chromatic quantization (12-TET) for whole-tone layouts

Allows semitones to be hit between whole-tone pads via software quantization.

New settings:
- chromatic_quantize: Enable 12-TET semitone snapping (default: false)
- whole_tone_bias: Adjust zone balance, range -1.0 to 1.0 (default: 0.0)
  - 0.15 recommended for LinnStrument speed bump surface

Requirements:
- LinnStrument Quantize=OFF, Quantize Tap=OFF, Quantize Hold=OFF
- This setting overrides hardware quantization with proper semitone support

Author: zitongcharliedeng

settings.ini.example

@@ -3,6 +3,12 @@
 
 [general]
 size=128
+
+; Software chromatic quantization (12-TET) - see settings.py for full documentation
+; REQUIRED: LinnStrument Quantize=OFF, Quantize Tap=OFF, Quantize Hold=OFF
+;chromatic_quantize=true
+;whole_tone_bias=0.4375
+
 ;velocity_curve=1.0
 ;lights=1,9,9,2,2,3,3,5,8,8,11,11
 ;split_lights=4,7,5,7,5,5,7,5,7,5,7,5

src/core.py

@@ -964,6 +964,37 @@ def cb_midi_in(self, data, timestamp, force_channel=None):
                 # NOTE: Synth must have MPE enabled for per-note slides
                 bend_val = decompose_pitch_bend((data[1], data[2]))
                 bend_val *= self.options.bend_scale
+                
+                # Software chromatic quantization (12-TET)
+                # Snaps pitch bends to nearest semitone for whole-tone layouts
+                # Requires: LinnStrument Quantize=OFF, Quantize Tap=OFF, Quantize Hold=OFF
+                if self.options.chromatic_quantize:
+                    # Semitone step size in normalized bend units
+                    # column_offset accounts for whole-tone layout (2 semitones per pad)
+                    semitone = 1.0 / (self.options.bend_range * self.options.column_offset)
+                    semitones = bend_val / semitone
+                    
+                    bias = self.options.whole_tone_bias
+                    
+                    if bias == 0:
+                        nearest = round(semitones)
+                    else:
+                        # Biased rounding to compensate for mechanical/surface differences
+                        # Positive bias = expand whole-tone zones, negative = expand semitone zones
+                        floor_semi = int(semitones) if semitones >= 0 else int(semitones) - 1
+                        frac = semitones - floor_semi
+                        
+                        # Even floor = whole tone (pad center), Odd = semitone (between pads)
+                        if floor_semi % 2 == 0:
+                            threshold = 0.5 + bias  # Positive bias raises threshold to semitone
+                        else:
+                            threshold = 0.5 - bias  # Positive bias lowers threshold to leave semitone
+                        
+                        threshold = max(0.05, min(0.95, threshold))
+                        nearest = floor_semi + 1 if frac >= threshold else floor_semi
+                    
+                    bend_val = nearest * semitone
+                
                 data[1], data[2] = compose_pitch_bend(bend_val)
 
                 if self.is_split():
@@ -1401,6 +1432,14 @@ def __init__(self):
             opts, "bend_scale", DEFAULT_OPTIONS.bend_scale
         )
 
+        # Software chromatic quantization (12-TET)
+        self.options.chromatic_quantize = get_option(
+            opts, "chromatic_quantize", DEFAULT_OPTIONS.chromatic_quantize
+        )
+        self.options.whole_tone_bias = get_option(
+            opts, "whole_tone_bias", DEFAULT_OPTIONS.whole_tone_bias
+        )
+
         # self.options.mpe = get_option(
         #     opts, "mpe", DEFAULT_OPTIONS.mpe
         # ) or get_option(

src/settings.py

@@ -109,5 +109,22 @@ class Settings:
     # octave splitting the linn and transposing octaves on the right side
     octave_split: int = 0
 
+    # Software chromatic quantization (12-TET)
+    # Snaps pitch bends to nearest semitone, allowing semitones between whole-tone pads.
+    # Without quantization, every note has slight microtonal errors from human imprecision.
+    # At this pad scale, you can only realistically aim for semitones or whole tones.
+    # Hardware quantization only snaps to pad centers (whole tones), missing semitones.
+    # This software quantization snaps to ALL 12 chromatic semitones.
+    # REQUIRED: Set LinnStrument Quantize=OFF, Quantize Tap=OFF, Quantize Hold=OFF
+    chromatic_quantize: bool = False
+    
+    # Whole tone bias: adjusts the rounding threshold between semitones and whole tones.
+    # Range: -1.0 to 1.0
+    #   0.0 = equal zones (50/50 split, standard rounding at 0.5 threshold)
+    #   Positive = larger whole-tone zones (need to aim closer to center to hit semitones)
+    #   Negative = larger semitone zones (easier to hit semitones accidentally)
+    # Recommended: 0.4375 for LinnStrument speed bump surface
+    whole_tone_bias: float = 0.0
+
 DEFAULT_OPTIONS = Settings()
 

src/util.py

@@ -129,3 +129,6 @@ def get_color(col):
     if col.startswith("#"):
         return webcolors.hex_to_rgb(col)
     return webcolors.name_to_rgb(col)
+
+
+