Credit Card-Sized, Open Source MIDI Controller with Affordable MIDI Out Connector
This open source software and hardware MIDI controller can be hacked with your own custom firmware.
If you want to add sound effects to your track, pick a MIDI controller rather than a keyboard. This open source, credit card-sized, USB-powered device is designed to control the level, pan, and modulation wheel of all the MIDI channels.
The brainchild of Sensai's Synthstuff, the MIDI controller differs from others as it gives the output of raw MIDI data through a TRS mini-jack or five-pin DIN-5 that's connected to a computer or synthesizer. According to its creator, "The controllers including old-fashioned MIDI OUT port are either way too big or way too expensive or way too old, thus, this one is both small and affordable."
Even though the board comes with installed firmware, in order to burn the future firmware on the MIDI controller board, you will need an Arduino Uno or any similar board that comes with an ICSP header. First, upload the "Arduino as ISP" example code on your Arduino and unplug the Arduino. Then, connect the ICSP headers of both the boards except for the RST of the MIDI controller. RST is connected to pin 10 of the board. More steps to get this done can be found in the GitHub repository.
You can also order your own with SMT components pre-soldered. To do this, you are required to upload zipped Gerber files to the shopping website with some other recommended changes (on GitHub). However, the MIDI controller can be purchased via Tindie for $30 plus shipping. The model is available in two MIDI OUT connectors with no change in pricing.