I like to notice, that the Gothic Choir now has a good video that shows how Gothic Choir seems in action. Please follow the link, hope you will enjoy - Gothic Choir for UE4 - YouTube
Gothic Choir at Marketplace - Gothic Choir in Blueprints - UE Marketplace
Gothic Choir is a Midi Audio-Visualisation Tool integrated with Unreal Engine 4.
Use your Midi Device like Midi Keyboard or Synth with Midi Connection to play with Gothic Choir or you can play using your mouse or pc keyboard (Shorcuts applied to E-P keys).
For playing with MIDI you need to have Midi Device (Midi Keyboard or Midi Pad and etc.) Especially this product works fine with Midi Keyboards or Hardware Synthesizers with MIDI and principle is like simple Sound Font Instrument or Virtual Instrument (VSTi) but in Unreal Engine 4 Virtual Space.
For use in other projects make sure the required plugin is enabled:
Plugins > Input Devices > MIDI Device Support