qmk_firmware/quantum/audio/audio.h

#ifndef AUDIO_H
#define AUDIO_H

#include <stdint.h>
#include <stdbool.h>
#include <avr/io.h>
#include <util/delay.h>
#include "musical_notes.h"
#include "song_list.h"
#include "voices.h"
#include "quantum.h"

// Largely untested PWM audio mode (doesn't sound as good)
// #define PWM_AUDIO

// #define VIBRATO_ENABLE

// Enable vibrato strength/amplitude - slows down ISR too much
// #define VIBRATO_STRENGTH_ENABLE

typedef union {
    uint8_t raw;
    struct {
        bool    enable :1;
        uint8_t level  :7;
    };
} audio_config_t;

bool is_audio_on(void);
void audio_toggle(void);
void audio_on(void);
void audio_off(void);

// Vibrato rate functions

#ifdef VIBRATO_ENABLE

void set_vibrato_rate(float rate);
void increase_vibrato_rate(float change);
void decrease_vibrato_rate(float change);

#ifdef VIBRATO_STRENGTH_ENABLE

void set_vibrato_strength(float strength);
void increase_vibrato_strength(float change);
void decrease_vibrato_strength(float change);

#endif

#endif

// Polyphony functions

void set_polyphony_rate(float rate);
void enable_polyphony(void);
void disable_polyphony(void);
void increase_polyphony_rate(float change);
void decrease_polyphony_rate(float change);

void set_timbre(float timbre);
void set_tempo(uint8_t tempo);

void increase_tempo(uint8_t tempo_change);
void decrease_tempo(uint8_t tempo_change);

void audio_init(void);

#ifdef PWM_AUDIO
void play_sample(uint8_t * s, uint16_t l, bool r);
#endif
void play_note(float freq, int vol);
void stop_note(float freq);
void stop_all_notes(void);
void play_notes(float (*np)[][2], uint16_t n_count, bool n_repeat, float n_rest);

#define SCALE (int8_t []){ 0 + (12*0), 2 + (12*0), 4 + (12*0), 5 + (12*0), 7 + (12*0), 9 + (12*0), 11 + (12*0), \
                           0 + (12*1), 2 + (12*1), 4 + (12*1), 5 + (12*1), 7 + (12*1), 9 + (12*1), 11 + (12*1), \
                           0 + (12*2), 2 + (12*2), 4 + (12*2), 5 + (12*2), 7 + (12*2), 9 + (12*2), 11 + (12*2), \
                           0 + (12*3), 2 + (12*3), 4 + (12*3), 5 + (12*3), 7 + (12*3), 9 + (12*3), 11 + (12*3), \
                           0 + (12*4), 2 + (12*4), 4 + (12*4), 5 + (12*4), 7 + (12*4), 9 + (12*4), 11 + (12*4), }

// These macros are used to allow play_notes to play an array of indeterminate
// length. This works around the limitation of C's sizeof operation on pointers.
// The global float array for the song must be used here.
#define NOTE_ARRAY_SIZE(x) ((int16_t)(sizeof(x) / (sizeof(x[0]))))
#define PLAY_NOTE_ARRAY(note_array, note_repeat, note_rest_style) play_notes(&note_array, NOTE_ARRAY_SIZE((note_array)), (note_repeat), (note_rest_style));


bool is_playing_notes(void);

#endif