I didn't want to spend 100$ on AKAI MPD. I thought I can make one myself.
So i bought a bunch of buttons, two 74151 multiplexers, an Arduino Uno and went to work.
The program is very simple. It scans through all buttons (two buttons at time thanks to two multiplexeres), debounces buttons if needed and sends midi command through serial port (source code in links).
On the other side of serial is PC with Hearless Serial to Midi software. This magnificent program converts serial input into midi commands. Then it can be used in all sorts of programs like FL Studio or ableton.
If I ever make second version of it I will
1. use better (connected with each other) cables
2. use shift registers to read all buttons state at once.
3. use better (more silent) buttons
Still it works like a charm and I'm left with 100$ in my pocket :)