Additional tracks that can be used for Audio or MIDI. From the Help:
Utility TracksBand-in-a-Box has 16 editable Utility tracks, which can be used for audio and/or MIDI. You can generate RealTracks on the Utility tracks, where you can hear and edit the audio RealTracks, or view and edit the RealCharts MIDI. You can record audio or import an audio file to the Utility tracks to play, edit, or harmonize the audio. You can copy or move audio, MIDI, or both from other tracks to the Utility tracks. You can record MIDI or import a MIDI file to the Utility tracks for playback, notation display, or editing.
Note: If a Utility track contains both audio and MIDI, the audio is audible and the MIDI is only for display purposes (e.g., transcription of the audio). If a Utility track contains only MIDI, then the MIDI is audible.