Hello Audio

Now that you can draw and move a sprite, the next step is sound.

This demo plays a short PSG jingle when you press A.

The code

#include <gba/bios>
#include <gba/interrupt>
#include <gba/keyinput>
#include <gba/music>
#include <gba/peripherals>

using namespace gba::music;
using namespace gba::music::literals;

namespace {

    // One-shot PSG jingle (SQ1). Press A to restart playback.
    // .press() applies staccato: each note plays for half duration, rest for half.
    // Compiled at 2_cps (2 cycles per second) for a snappy tempo.
    static constexpr auto jingle = compile<2_cps>(note("c5 e5 g5 c6").channel(channel::sq1).press());

} // namespace

int main() {
    gba::irq_handler = {};
    gba::reg_dispstat = {.enable_irq_vblank = true};
    gba::reg_ie = {.vblank = true};
    gba::reg_ime = true;

    // Basic PSG routing for SQ1 on both speakers.
    gba::reg_soundcnt_x = {.master_enable = true};
    gba::reg_soundcnt_l = {
        .volume_right = 7,
        .volume_left = 7,
        .enable_1_right = true,
        .enable_1_left = true,
    };
    gba::reg_soundcnt_h = {.psg_volume = 2};

    gba::keypad keys;
    auto player = music_player<jingle>{};

    while (true) {
        gba::VBlankIntrWait();
        keys = gba::reg_keyinput;

        if (keys.pressed(gba::key_a)) {
            player = {};
        }

        player();
    }
}

What is happening?

1. We set up VBlank + interrupts as in earlier chapters.
2. We enable PSG output with reg_soundcnt_x, reg_soundcnt_l, and reg_soundcnt_h.
3. note("c5 e5 g5 c6").channel(channel::sq1).press() builds a staccato pattern (each note plays half duration, rests half), ensuring the jingle ends in silence naturally.
4. compile<2_cps>(...) compiles at 2 cycles per second (4x faster than the default 0.5 cps), making the jingle snappy and brief.
5. music_player<jingle> advances once per frame, dispatching note events.
6. Pressing A resets the player with player = {}, restarting the jingle from the beginning.

Next step

Move on to Registers & Peripherals, then dive deeper into Music Composition.