tone
opm_set_key(int channel, int tone)
writeopm(0x28 + channel, tone >> 8);
writeopm(0x30 + channel, tone & 0xff);
spkr_attach(device_t self, void (*tone)(device_t, u_int, u_int))
sc->sc_tone = tone;
tone_t tone;
tone.frequency = vb->pitch;
tone.duration = vb->period / 10;
spkrioctl(sc->sc_spkr, SPKRTONE, &tone, 0, curlwp);