There are natural \"beat\" frequencies created from intonational variations between the various players - this is most likely what you are hearing. If this particular note is not acceptable in the context of a particular passage then open the .gig file in the Instrument Editor, highlight the region (A4) and hit the \"delete\" button on your computer keyboard. Then move your cursor to the left edge of the A#4 region, click and hold, and drag the edge of the A#4 region to the left to cover the space of the (now missing) A4. Let go and save. This will replace the A4 sample with the transposed A#4 sample. It may be more suitable to your needs. This technique can often be used to deal with any particular note that doesn’t seem to quite “work” in a given situation.