[acheron]

I go to local performances of baroque-era and somewhat earlier music regularly. I have noticed on occasion in a small vocal performance that has 2 people per part, occasionally a female contralto is paired with a male tenor. (I don’t know enough to know how that works as far as needing to modify the original parts or not.)

Though conversely I’ve also seen a male countertenor paired with a female alto, so maybe it’s just generally “who’s available for this performance” rather than an issue with a general shortage.

[yellowapple]

I'm no professional choir composer/arranger by any means, but my impression from listening to and reading my fair share of choir music is that there's enough overlap between alto and tenor ranges for them to be able to cross over into one anothers' parts in a pinch. It's pretty rare for a composer to write a song with simultaneous use of the altos' upper range and the tenors' lower range, so there probably wouldn't be much need to rewrite anything to make that work.