snd_opl4_do_for_channel
snd_opl4_do_for_channel(opl4, chan, snd_opl4_update_vibrato_depth);
snd_opl4_do_for_channel(opl4, chan, snd_opl4_update_volume);
snd_opl4_do_for_channel(opl4, chan, snd_opl4_update_pan);
snd_opl4_do_for_channel(opl4, chan, snd_opl4_update_volume);
snd_opl4_do_for_channel(opl4, chan, snd_opl4_update_vibrato_depth);
snd_opl4_do_for_channel(opl4, chan, snd_opl4_update_pitch);