A typical MIDI track header looks like this:

To see the full set of MIDI track controls, you need to increase the track height beyond the default. MIDI tracks show only a few of the control elements when there is insufficient vertical space.

A MIDI track has the same basic controls as an audio track, with the addition of two extra elements. The set of buttons below the main track controls the MIDI channel(s) that will be visible in the editor. A MIDI track's data may span any number of the 16 available MIDI channels, and sometimes it is useful to view only a subset of those channels; different instruments may, for example, be put on different channels. Clicking on a channel number toggles its visibility.

To the right of the MIDI track controls is a representation of a piano keyboard called the scroomer. This performs a couple of functions. The scrollbar controls the range of pitches that are visible on the track, as visualized by the piano keyboard.
Drag the body of the scrollbar up and down to display higher or lower pitches.
Drag the scrollbar handles to zooms in and out and increase and decrease the range of visible pitches.
clicking on the piano plays the corresponding MIDI note for reference.

To edit the contents of a MIDI track see Edit MIDI.