Note Tracks

From Audacity Manual

Note Tracks display data from MIDI files - these can be imported with the File > Import MIDI... command. Note Tracks cannot currently be played, but can be cut-and-paste edited, then exported using the File > Export MIDI command.

Despite the currently limited functionality, it can be useful to visually compare a given MIDI file with a sampled audio file (such as WAV) of the same music.