BASS_ATTRIB_MIXER_VOL attribute

Master volume level of a mixer.

BASS_ChannelSetAttribute(
    HSTREAM handle,
    BASS_ATTRIB_MIXER_VOL,
    float volume
);

Parameters

handle	The mixer stream handle.
volume	The volume level... 0 = silent, 1.0 = normal/default, above 1.0 = amplification.

This attribute differs from the BASS_ATTRIB_VOL attribute in that it changes the level of the generated data, not just playback of it.