Look here for a detailed description of each classes, prefabs, methods, attributs, …

Prefabs available with the Free version

• MidiFilePlayer: play music from a MIDI file with a full control of  speed, position, quantization, channel, instrument, …
• MidiStreamPlayer: create music from your algorithm. Generative music is at your fingertips. Generate each MIDI Events to build your music. 
• MidiFileLoader: load a MIDIfile for analysis or processing purpose by accessing to all the MIDI events: note, tempo, text, instrument, …

Prefabs available with the Pro version

• MidiListPlayer: play music from a list of MIDI files, overlap between MIDI, play part of a midi, loop …
• MidiExternalPlay: play a MIDI directly from the Web or anywhere on the desktop.
• MidiInReader: read MIDI events from a MIDI keyboard, play directly, or do all that you want with the MIDI events.
• MidiSpatializer: play music from a MIDI files with the spatializer ready for a 3D environment where each instruments can be localized.

There is surely a prefab for your need! All you have to do is to add one of this prefab to your scene.