Signal-Based Auto Record is a Max for Live device (.amxd). It requires Ableton Live 8.3 or newer and Max/MSP 5.1 or newer.
Set a signal Threshold over which recording will automatically begin.
The Tail designates the number of seconds recording will continue for after the signal has fallen back below the Threshold.
With Breaks Loop checked, recording will restart from the last place the cursor was set. With it unchecked, recording will begin where it left off.
The six red and green check boxes can be set to designate whether the Global Record, Play, and Follow buttons turn on or off when the signal has risen above the Threshold or when the Tail has run its course, respectively. Generally you will want them all selected.
This device works well in the Master Audio Track although it can be placed in any track.
Click the button labeled 'On' to switch the device to bypass mode which essentially turns it off. Click again to turn it back on.