• PSG (psg.h)
• sound API
• psgT(hz)
• set_psg (reg, val)
• get_psg (reg)
• psg_init()
• psg_tone()
• psg_noise (period)
• psg_volume(channel, volume)
• psg_envelope(waveform, period, channels)
• psg_channels(tone_channels, noise_channels)
• psg_tone_channels()
• psg_noise_channels()