Solo performer friend was using a Boss OC-3 to add bass notes to their guitar-only set. The OC-3 can grab the bass note of a chord played and generate that pitch alone, but you have to play your chords clearly and simply for it to track well.

This signal splitter has a single guitar input that is buffered and sent:
-unaltered to the G output
-high frequencies are filtered out and sent to the B output (which can then feed the OC-3 or other pedal that is looking for low frequency pitches).
The Freq knob changes the filter cutoff frequency.