On the Pioneer Toraiz SP-16, if I remember correctly, you can assign the audio input to one pad/track, then record audio from this track into the other pads/tracks. This means you can mute the audio input by tapping its pad, and if you tap both pads together then you could mute the input as the recorded loop started for transitioning from the audio input into the recorded loop. Would something like this be possible? (not sure how well I explained that)