This USB audio interface from the Austria-based ... with an XLR microphone input and a Hi-Z input for a keyboard or guitar. The interface has most of the tools you need to capture voices and ...

1-in 6-out】The MIDI Thru-6 Box provide 1 MIDI in and 6 MIDI out midi interface. Smooth MIDI signal ... which is power by 5V DC USB power supply. It can works with most MIDI products.

[Pierre] over on the Pure Data mailing list has a proof-of-concept working that uses the Raspi as a guitar effects processor ... tutorials and verified USB audio interfaces later.