As far as I can tell, BASS_SYNC_END can only be used as mixtime sync on channels that are fed into mixers, because they will always be decoding channels. Is there any way to know when the end of a channel that is fed into a mixer is effectively heard? If not, would it be possible to provide a new sync type for mixer channels that could provide this information? Something like BASS_ChannelSetSync(mixerHandle, BASS_SYNC_END, channelHandle, proc, user) maybe?