scook
I do not have an extra MIDI looping software on my machine. I do as jma, have input echo and record both the track with MIDI Guitar and the synth midi track.
I'm pretty sure I tried that.
However, with loopBe1 enabled I do not need to have record or echo on for the MIDI Guitar (audio) track to now trigger the MIDI track and thus the synth. In fact I record an audio of the guitar track and did not record the MIDI and upon playback the audio track drove the synth.
So, it seems you can just apply MIDI Guitar (as a synth FX bin insert) to any previously recorded guitar track and drive any synth (YMMV on the accuracy bssed on the quality of the recorded track).