If you are trying to tempo match beats on the playlist, or even in the mixer (waveforms or delay times etc) a two stage solo, which on first press cut the solo'd faders signals to just - %75 then on second press the channels went to full mute, it would massivly help tempo syncing by ear. it's a standard for DJs to have similar levels in either headphones.
The first stage of mute would allow you a partial signal to tempo match to, making it easier to distuingwish one signal from another, or a group of signals.
2 stage solo.
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