Performance (MIDI) View Buttons

The following buttons in Composer's toolbar enable you to view the underlying performance (MIDI) data in a musical score:

These buttons are for viewing, but not editing, the performance data. You can toggle the view of these graphs on or off while working with other tabs by clicking the button "on" or "off."

Why would you want to just view the performance data, but not edit it?  The most common reason is that as you are annotating certain types of music symbols in the score, such as dynamic marks, accent marks, and tempo marks, it is very useful to see the underlying performance data.  Some examples are illustrated in this topic.

If you want to edit, not just view the performance data, then click one of the palette tabs for Piano Roll, Note Velocity, or GraphOverNotestm:

Piano Roll (Note Timing)

When you click the Piano Roll button, Composer will display piano roll notation, such as illustrated here:

The piano roll notation graphically shows the timing of notes, specifically, their MIDI note-on and note-off locations. The above example illustrates how you might use the piano roll view of note timing to determine which notes should have staccato marks.
 

Velocity Vectors (Note Loudness)

When you click the Note Loudness button, Composer will display note velocity vectors, such as illustrated here:

The note velocity vector graphically shows how loud the notes are. The above example illustrates how you might use the note velocity vectors to determine which notes should have "strong accent" ( > ) marks.

Tempo, Volume, Pan, Pitch Bend, Sustain Pedal, MIDI Controllers (Graph View)

When you click the Graph View button, Composer will display a graph, such as the following for the tempo in a theme section of George Gershwin's Rhapsody in Blue:

You might use the above tempo graph to determine where to add an accelerando mark, or perhaps a phrase mark (slur). For details, see Viewing and Editing Graphs of Musical Performance.