How to make velocity of louder note supersede velocity of quieter note

Hello everyone

Our choir is going to try a Zoom session (obvious muted while people sing), and we decided to just play the sheet music straight from MuseScore with a shared screen. (The alternative being to show a PDF and play an MP3, but then we can't control from where we begin.)

Usually, I put the four choir parts (soprano, alto, tenor and bass) on four different instruments (it makes creating MIDI files a lot easier), but since we now have an audience that's going to look at the music in MuseScore, I copied the soprano and alto parts onto the one instrument and the tenor and bass parts onto the other instrument. In MuseScore, Soprano is voice 1 and alto is voice 2, tenor is voice 1 and bass is voice 2, so I'm able to change the settings for e.g. soprano and alto even though they're on the same instrument.

Now, I would like soprano to play at +100 velocity offset and the other parts at -60. But: I find that if both soprano and alto have the same note, MuseScore always makes the quieter velocity (in this case alto) supersede the louder velocity (in this case soprano). I tried first setting all notes to -60 and then setting the soprano to +100, and I tried first setting all notes to +100 and then setting the alto to -60, but alas: the notes that are shared by both soprano and alto always play at -60.

What I want is for the loudest velocity to be the one that is used if two notes are the same note. How can I accomplish this?

Thanks
Samuel

(PS. The way I usually make MP3 files with one part louder than the other is by adding dynamics to the instruments, e.g. fff to the loud instrument and ppp to the others, but I can't do that now since each instrument has two choir parts on it.)