fix: resolve nthModalPitch broken for sharp keys like D#

buildScale converts notes like F→E♯ and C→B♯ to avoid duplicate
letter names, but playNthModalPitch and ScaleDegreeBlock lookup these
notes in NOTESSHARP which doesn't contain them, returning -1 and
breaking the semitone calculation.

Fix: resolve special notes (E♯→F, B♯→C, C♭→B, F♭→E) via
EQUIVALENTNATURALS before looking up in NOTESFLAT/NOTESSHARP.

Affected: playNthModalPitch (PitchActions.js:246) and
ScaleDegreeBlock (PitchBlocks.js:2008)

Related to #7171

Author: 021nirav-blip

js/blocks/PitchBlocks.js

@@ -20,7 +20,7 @@
    YSTAFFNOTEHEIGHT, MUSICALMODES, keySignatureToMode, ALLNOTENAMES,
    nthDegreeToPitch, A0, C8, calcOctave, SOLFEGECONVERSIONTABLE,
     NOTESFLAT, NOTESSHARP, NOTESTEP, scaleDegreeToPitchMapping,
-    INTERVALVALUES
+    INTERVALVALUES, EQUIVALENTNATURALS
  */
 
 /* exported setupPitchBlocks */
@@ -2005,9 +2005,11 @@ function setupPitchBlocks(activity) {
                     );
                     let semitones = ref;
 
-                    semitones += NOTESFLAT.includes(note)
-                        ? NOTESFLAT.indexOf(note) - ref
-                        : NOTESSHARP.indexOf(note) - ref;
+                    const resolvedNote =
+                        note in EQUIVALENTNATURALS ? EQUIVALENTNATURALS[note] : note;
+                    semitones += NOTESFLAT.includes(resolvedNote)
+                        ? NOTESFLAT.indexOf(resolvedNote) - ref
+                        : NOTESSHARP.indexOf(resolvedNote) - ref;
 
                     /** calculates changes in reference octave which occur a semitone before the reference key */
                     const deltaOctave = isNegativeArg

js/blocks/__tests__/PitchBlocks.test.js

@@ -160,6 +160,12 @@ describe("setupPitchBlocks", () => {
         global.NOTESSHARP = ["C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B"];
         global.NOTESFLAT = ["C", "Db", "D", "Eb", "E", "F", "Gb", "G", "Ab", "A", "Bb", "B"];
         global.NOTESTEP = { C: 1, D: 3, E: 5, F: 6, G: 8, A: 10, B: 12 };
+        global.EQUIVALENTNATURALS = {
+            "E\u266F": "F",
+            "B\u266F": "C",
+            "C\u266D": "B",
+            "F\u266D": "E"
+        };
         global.SOLFEGECONVERSIONTABLE = {
             C: "do",
             D: "re",

js/turtleactions/PitchActions.js

@@ -25,7 +25,7 @@
    nthDegreeToPitch, SHARP, FLAT, pitchToFrequency, SOLFEGENAMES1, SOLFEGECONVERSIONTABLE,
    numberToPitch, ACCIDENTALNAMES, ACCIDENTALVALUES, NOTESFLAT, NOTESSHARP, NOTESTEP, MUSICALMODES,
    keySignatureToMode, getInterval, EFFECTSNAMES, NANERRORMSG, frequencyToPitch,
-   MusicBlocks, Mouse, isCustomTemperament
+   MusicBlocks, Mouse, isCustomTemperament, EQUIVALENTNATURALS
 */
 
 /*
@@ -243,9 +243,10 @@ function setupPitchActions(activity) {
 
             const [note, _offset] = nthDegreeToPitch(tur.singer.keySignature, scaleDegree);
             let semitones = ref;
-            semitones += NOTESFLAT.includes(note)
-                ? NOTESFLAT.indexOf(note) - ref
-                : NOTESSHARP.indexOf(note) - ref;
+            const resolvedNote = note in EQUIVALENTNATURALS ? EQUIVALENTNATURALS[note] : note;
+            semitones += NOTESFLAT.includes(resolvedNote)
+                ? NOTESFLAT.indexOf(resolvedNote) - ref
+                : NOTESSHARP.indexOf(resolvedNote) - ref;
             /** calculates changes in reference octave which occur a semitone before the reference key */
             const deltaOctave = Math.floor(number / modeLength);
             /** calculates changes in octave when crossing B */

js/turtleactions/__tests__/PitchActions.test.js

@@ -43,7 +43,8 @@ Object.assign(global, {
     NOTESTEP: musicUtils.NOTESTEP,
     MUSICALMODES: musicUtils.MUSICALMODES,
     SHARP: musicUtils.SHARP,
-    FLAT: musicUtils.FLAT
+    FLAT: musicUtils.FLAT,
+    EQUIVALENTNATURALS: { "E\u266F": "F", "B\u266F": "C", "C\u266D": "B", "F\u266D": "E" }
 });
 
 global.NANERRORMSG = require("../../logo").NANERRORMSG;

js/utils/__tests__/musicutils.test.js

@@ -2046,6 +2046,89 @@ describe("pitchToFrequency", () => {
     });
 });
 
+describe("pitchToFrequency cents edge cases", () => {
+    global.TWELTHROOT2 = 1.0594630943592953;
+    global.TWELVEHUNDRETHROOT2 = Number("1.0005777895065549");
+    global.A0 = 27.5;
+
+    it("12-EDO regression: cents formula matches standard 12-EDO", () => {
+        // When temperament is 12-EDO and cents is 0, result must equal standard 12-EDO frequency
+        const result0 = pitchToFrequency("A", 4, 0, "C");
+        expect(result0).toBe(A0 * Math.pow(TWELTHROOT2, 48));
+
+        // With cents and 12-EDO, uses 1200-EDO formula
+        const result50 = pitchToFrequency("A", 4, 50, "C");
+        expect(result50).toBe(A0 * Math.pow(TWELVEHUNDRETHROOT2, 48 * 100 + 50));
+    });
+
+    it("19-EDO cents: explicit formula matches implementation", () => {
+        // A4 in 19-EDO = pitchNumber 76 (4 * 19)
+        // freq = A0 * 2^(1/(19*100))^(76*100 + cents)
+        const result0 = pitchToFrequency("A", 4, 0, "C", "equal19");
+        const expected0 = A0 * Math.pow(2, 1 / (19 * 100)) ** (76 * 100);
+        expect(result0).toBeCloseTo(expected0, 4);
+
+        const result50 = pitchToFrequency("A", 4, 50, "C", "equal19");
+        const expected50 = A0 * Math.pow(2, 1 / (19 * 100)) ** (76 * 100 + 50);
+        expect(result50).toBeCloseTo(expected50, 4);
+    });
+
+    it("31-EDO cents: explicit formula matches implementation", () => {
+        // A4 in 31-EDO = pitchNumber 124 (4 * 31)
+        const result0 = pitchToFrequency("A", 4, 0, "C", "equal31");
+        const expected0 = A0 * Math.pow(2, 1 / (31 * 100)) ** (124 * 100);
+        expect(result0).toBeCloseTo(expected0, 4);
+
+        const result100 = pitchToFrequency("A", 4, 100, "C", "equal31");
+        const expected100 = A0 * Math.pow(2, 1 / (31 * 100)) ** (124 * 100 + 100);
+        expect(result100).toBeCloseTo(expected100, 4);
+    });
+
+    it("handles large positive cents in 12-EDO", () => {
+        // 1199 cents ~ almost one octave above
+        const result = pitchToFrequency("A", 4, 1199, "C");
+        const expected = A0 * Math.pow(TWELVEHUNDRETHROOT2, 48 * 100 + 1199);
+        expect(result).toBeCloseTo(expected, 4);
+    });
+
+    it("handles large negative cents in 12-EDO", () => {
+        // -100 cents = one semitone flat
+        const result = pitchToFrequency("A", 4, -100, "C");
+        const expected = A0 * Math.pow(TWELVEHUNDRETHROOT2, 48 * 100 - 100);
+        expect(result).toBeCloseTo(expected, 4);
+    });
+
+    it("handles cents at different octaves with temperament", () => {
+        // C5 in 19-EDO: pitchNumber = 5*19 + 0(C) - 9(A offset) = 86
+        const result = pitchToFrequency("C", 5, 30, "C", "equal19");
+        const expected = A0 * Math.pow(2, 1 / (19 * 100)) ** (86 * 100 + 30);
+        expect(result).toBeCloseTo(expected, 4);
+    });
+
+    it("12-EDO regression: cents with unequal temperaments", () => {
+        // Default equal temperament with cents should match 12-EDO cents formula
+        const result = pitchToFrequency("A", 4, 75, "C");
+        const expected = A0 * Math.pow(TWELVEHUNDRETHROOT2, 48 * 100 + 75);
+        expect(result).toBeCloseTo(expected, 4);
+    });
+});
+
+describe("frequencyToPitch cents with 12-EDO regression", () => {
+    it("returns 0 cents for exact 12-EDO pitches", () => {
+        expect(frequencyToPitch(440)[2]).toBe(0);
+        expect(frequencyToPitch(261.63)[2]).toBe(0);
+        expect(frequencyToPitch(523.25)[2]).toBe(0);
+    });
+
+    it("detects small cents deviation in 12-EDO", () => {
+        // 441 Hz = 440 * 2^(1/1200) ≈ A4 + 1 cent
+        const freq = 440 * Math.pow(2, 1 / 1200);
+        const result = frequencyToPitch(freq);
+        expect(result[2]).toBeGreaterThan(0);
+        expect(result[2]).toBeLessThan(2);
+    });
+});
+
 describe("noteToFrequency", () => {
     global.TWELTHROOT2 = 1.0594630943592953;
     global.TWELVEHUNDRETHROOT2 = Number("1.0005777895065549");