I already said that when pressing F4, the channel 16 highlights.
This may sound the same, but when cursor is either at the ch 10 or ch 16, and press F4, the highlight responds to ch 16.
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Prior discussion <here> (https://forum.noteworthycomposer.com/?topic=7242.0).
During Record (http://ntworthy.com/nwc2/help/MNU_MIDIRECORD.htm) (F4), it seems to me that the pianobar responds to note on/off on MIDI channel 16.
With the sample file: Meistersinger.nwc, record will highlight the notes from the 'Basses' staff on the pianobar. If that staff is muted or deleted, nothing is highlighted on the pianobar.
I have no opinion on why this occurs or whether it has any use.