Ableton Live M4L Audio Device.
Waveguide / Karplus Strong technique / Delay line inspired by Make Noise Mysteron, Meng Qi Karp, etc. It can accept any audio signal input.
About midi external: when using in Windows, imp.midi in cannot use any port that the host application (Max or Ableton Live) is also using. Any ports required to be used with imp.midi should be disabled in Max/Ableton MIDI preferences. This is due to Windows lacking a native multi-client MIDI driver.