Having a group of singers who can sing well together isn’t the special part.
Thousands upon thousands of singers have learned to master vocal jazz and choral music over the decades, singing tight harmony in tune. As hard as it is, it’s not that special.
What is special is finding a group that can get along and agree on goals and aims, long term.
What is special is finding a group that can think as one, making it feel less like 5 simultaneous singers than like a 5-headed soloist.
What is special is agreeing about interpretation, down to the tiniest detail.
What is special is finding people who all love practice equally well.