AgsMutable — unique access to recalls
AgsMutable is implemented by
AgsBufferChannel, AgsCopyChannel, AgsMuteAudio, AgsMuteChannel and AgsPlayChannel.
The AgsMutable interface gives you a unique access to recalls. Its
purpose is to mute playback.
ags_mutable_set_muted (AgsMutable *mutable,
Mute an AgsRecall instance.
if TRUE then muted, else playing