For the last 3 month I've worked on a MIDI live looper tool, and now it reach slowly a usable stage.
It is Virtual MIDI keyboard which you could play as usual with the PC keyboard or mouse, but it feature as well jack and ALSA MIDI input, so you could play it with your external MIDI keyboard as well. You could easily connect the inputs over a small connection menu.
It include a 16 channel live looper were you could record a channels while the other channels play. So you could rapidly create a backing track on some channels and then play along. You could clear each individual channel and re-record it when you are not happy with the result.
You could as well load a MIDI file as backing track and play along.
Anyway, the first recorded (or loaded) loop becomes the master loop and all following records will be synced in timeline to it.
When you would save your work you could save it as MIDI file and load it into the DAW of your choice to edit it if you need, or, reload it later to play along with it again.
You could connect the MIDI output to a synth of your choice, or, use the internal connected fluidsynth engine to load a sound-font and select the instruments for your channels.
If you like to give it a go, here you get it:
https://github.com/brummer10/Mamba
follow the build instruction on the bottom of the page, it's really easy to build and has a low dependency list.
Mamba - MIDI live looping
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