Quantity   Component name
1 × CTK-480 Cheap second hand keyboard/synthesizer.
1 × MIDI Shield Breakout Board for Arduino uno r3 2560 AVI PIC Digital Interface Just need the connector really, but it seemed cheeper.
1 × USB to midi
1 × npn invert the signal.
2 × resistors one for the p in npn, and one for the 5v pullup.