RtMidi is a set of C++ classes (RtMidiIn, RtMidiOut, and API specific classes)
that provide a common API (Application Programming Interface) for realtime MIDI
input/output across Linux (ALSA, JACK), Macintosh OS X (CoreMIDI, JACK), and
Windows (Multimedia Library) operating systems. RtMidi significantly simplifies
the process of interacting with computer MIDI hardware and software. It was
designed with the following goals:
* object oriented C++ design
* simple, common API across all supported platforms
* only one header and one source file for easy inclusion in programming projects
* MIDI device enumeration

WWW: https://github.com/thestk/rtmidi