Midi to +5V Trigger signals for Drum Machine

Hi, I am trying to convert midi to 8-10 different +5V trigger signals for a Roland TR-77 drum machine.
The TR-77 requires a -12V trigger signal and I have already built a circuit that can convert the +5V signal from the digital output of the arduino to a -12V trigger. I would appreciate some help/insight into how to do the midi to +5V part of this project?