Muting and Soloing Outputs in the Instruments Mixer Window Outputs across MIDI and Audio Tracks are muted and/or soloed by temporarily sending Controller 7s (Volume) with values of 0. Because Metro is sending controller information, its possible to mute and unmute a sustaining MIDI note event without having to physically retrigger it. Click on an Outputs Mute or Solo button in order to mute or solo it; click the Mute or Solo button again to unmute/unsolo the Output. Note: Using the Mute and/or Solo buttons within the Tracks window will not yield the same results as the Instrument Mixer windows Mute and/or Solo buttons, especially when working with long sustained note durations. Important: Please read Using Outputs, Ports and Faders, if you haven't done so; it explains in detail how to set up faders and use them to control aspects of playback, as well as how to record Controller events.