This is a trick my Dad used to use with his choirs when he wanted to clean up the rhythmic synchronization.
Sing most notes staccato to ‘plink’. The only exception to this is eighth notes or sixteenth notes which can be sung to ‘plink-a plink-a….’ Not only does this help the rhythm, it’s also hilarious – which is always useful when singers are becoming frustrated with everyone else’s sense of rhythm.
This exercise immediately shows up any sections that are out of synch.
When everything is cleaned up using ‘plink’, I ask the singers to use the words, but still sing staccato for a few times through, before going back to the more legato style.
I was singing with a group of local musicians last night, working on the Bach motet Komm Jesu Komm. ‘Plink’ works really really well with Bach – it makes revelling in the counterpoint so much fun!