Hi Mark,
Just returned home and saw your email and this post referring to the Trumpet Soloist Vibrato....

I cannot reproduce the 'problem' to which you refer !! I've listened to the Trumpet Soloist sound with no Transpose, and the note C and Db sound essentially the same as far as the vibrato is concerned....
I tried transposing to Db and still cannot hear any difference in the vibrato, when pressing the 'C' and 'Db' note keys....

I wonder if Mike's KN7000 produces the effect you are hearing??