[Joonas] became frustrated with cheap but crappy MIDI to USB converters, and the better commercial ones were beyond his budget. He used a Teensy LC to build one for himself and it did the job ...
[TheSpodShed] decided to whip up a USB MIDI interface for the chip, with the help of the Arduino Pro Micro. The Arduino Pro Micro is a Sparkfun creation, using the ATmega32U4 microcontroller.