ddmyx/scripts/AudioManager/AudioManager.gml

function bgm_play(_key)
{
    var _mus = oAudioManager.bgm_map[$ _key];
    if audio_is_playing(oAudioManager.bgm_current)
        audio_stop_sound(oAudioManager.bgm_current);
    oAudioManager.bgm_current = audio_play_sound(_mus, 0, true);
    audio_sound_gain(oAudioManager.bgm_current, oAudioManager.bgm_volume, 0);
}

function bgm_stop()
{
    audio_stop_sound(oAudioManager.bgm_current);
    oAudioManager.bgm_current = noone;
}

function sfx_play(_key, _pitch_vary = 0.1, _vol_vary = 0.1)
{
    var _sfx = oAudioManager.sfx_map[$ _key];
    var _inst = audio_play_sound(_sfx, 1, false);
    
    var _pitch = 1.0 + (random(_pitch_vary * 2) - _pitch_vary);
    var _vol = oAudioManager.sfx_volume * (1.0 - random(_vol_vary));
    
    audio_sound_pitch(_inst, _pitch);
    audio_sound_gain(_inst, _vol, 0);
    return _inst;
}