Amazing what a difference a good dose of rest will make.
Ready to get to work, and now only lacking the time (in the short term) to plant the ideas onto paper. (C'est-à-dire, life has returned to normal.) Ideas flowing both for the piece I've been asked for, for violin and harpsichord, and for a hitherto-unimagined jeu d'esprit involving a sequence of musical quotation.
But for now: off to work with my splendid little choir.