I've had the opportunity to play with a choir recently and through the process I've learned a few things.
A big part of playing with a choir is to help the choir keep in time (depending on how professional they are)
Sometimes you might only play a simple phrase or section in a tune. For example in Elenor Rigby there is a section where there is a Cello that does a straight Bb Major run (this might be the only part you need to play)
Being able to fill out the instrumentatal sections is often a requirement, especially if playing against a simple backing track that might just have chords.
Be careful with counter melodies in you bass lines as you dont want to clash with the choir or over accentuate certain parts.
Less is more - sometimes just root notes is enough
Im including a couple of tunes I performed recently for a choir to give you some ideas as to how I approached playing.
The Chain by Fleetwood Mac - audition to play with 'Choir For Fun' Mentone - Australia (2025)
A Thousand Years (Christina Perri) - Choir For Fun (Mentone Australia) (2025)