A recent online discussion centered around vocal jazz ensemble singers losing track of their rhythmic accuracy when their rhythm section joined them. Assuming that the rhythm section is playing well in time, and that the singers have rehearsed thoroughly and are capable of the accuracy, here’s the most likely culprit.
The singers are abrogating rhythmic responsibility to the instrumentalists. Once a percussive instrument joins singers – drums certainly, or even piano, singers are particularly likely to assume that they are no longer responsible for keeping track of the time.
I try to avoid a value judgement word like “lazy” – and I don’t think that’s exactly it, either, though the results can give that impression – a “lazy rhythmic energy” vibe. Instead, it’s more as if your vocal ensemble says “the band’s got this” and plans to float over the groove the band brings. To imprecise results.
I routinely remind my vocal jazz ensemble not to let anyone else be in charge of their rhythmic precision – not me, not the band, not another singer.