Is there a way to include spoken rhythmic text on the staff (using notes and lyrics) without the notes playing a tone?
Note Properties (http://ntworthy.com/nwc2/help/TAB_SNGNOTEPROPERTIES.htm): Muted
Or if you want a sound but not a musical tone, set the staff to MIDI channel 10. That's the percussion channel. Setting notes to different written pitches there changes timbre, not pitch. (If you need the staff to be part musical tones and part nonmusical sounds, you'll have to layer two staves together, one set to MIDI channel 10 and the other set to any other channel.)