(The MIDI channel buttons are all hidden on this keyboard.)

This is a MIDI channel button.

The dot above this button indicates this is the current channel; if you click the piano keys, Chroma will send MIDI notes on this channel.

This is a MIDI channel button.

Since it is off, the keyboard window will not display MIDI notes for this channel.  Click or shift–click the button to select it.

This is a MIDI channel button.

Since it is on, the keyboard window will display MIDI notes for this channel.

This is the MIDI controller wheel.

To change the controller for the current channel, drag this slider with the mouse.

This is a piano key.

It will display incoming MIDI notes from all active MIDI channels.

Click the key to play a note.  Dragging the mouse left or right bends the note, while dragging up or down applies aftertouch.

This is a Chroma keyboard window.

Chroma is a MIDI Manager application that displays MIDI note information in a colorful, graphical way.

You can also use Chroma to play music by clicking on the piano keys.