Larry,

I have used the vocal harmony to create my version of "The Four Freshmen", so as long as you stick to four note chords (like I mentioned before) it is OK to have as many chord changes per bar (max. 4, due to the limitations of BB) as you like. *)

However when you would sing the notes E, F, G over e.g. a Cmaj7 chord, the other voices will only change at the E and the G.
At a half step move (E to F) the other notes of the harmony stay put.
So you might want to reharmonize with passing chords; in this cage e.g. Cmaj7 (for the E melody note), Ddim7 or Dm7 (the F) to C6 (the G).

Brgds,
Tonnie

In the past I have posted a message on how to let BB play three chords over the half of a 4/4 bar. Like for instance in bar 5 of "It`s a Blue World" by the Four Freshmen.