The general advice for this type of Finale documents is that you set the “real” time signature to the biggest time signature.

In this case 12/8.

For the solo part, in the Staff Attributes, in the pane Independent Elements, select Time Signature.

Now you can use the Time Signature Tool to give the solo part a different time signature.

From here there are two solutions, both with rhythmically correct playback:

A. In the solo part, change the time signature to 4/4.

This solution plays back with correct rhythms, but you may experience difficulties with the precise placement of hairpins in the solo part.

B. In the solo part, change the time signature so that it displays as 4/4 (while the “real” time signature still is 12/8).

Enter the solo part’s notes as hidden tuplets.

Each measure can be one big (hidden) tuplet of {4 Quarters in the space of 6 Quarters}.

Unfortunately, solution A didn't playback correctly. This is what I had already done.

Option B was a bit of work to convert all the measures to one big hidden tuplet, with the "real" time signature hidden. But, it seems to have worked. So, thank you!

… I can't figure out how to get it to play back that way …

… solution A didn't playback correctly …

It is not clear to me what was wrong with the playback.

- Were the rhythms incorrect?

- Was the tempo incorrect?

- Or?