Is there a notational term for a drowsy tempo / feel?
How to notate a yawn?
How to indicate the breathy release at the end of a yawn? (Not just a comma-indicated “breath” of a pause.)
An Italian friend suggested assonnato or sonnolento for drowsy or sleepy. Sure enough, those terms are in Dolmetsch's music dictionary, which seems to include just about every word known to German, Italian and Spanish speakers, but not at Wikipedia's Glossary of musical terminology.
This came up in arranging, for bassoon and euphoniums, an overly dramatic version of Mendelssohn's Nocturne from Midsummer Night's Dream with an emphasis on the characters' yawning and falling asleep. The original tranquillo is too sweet and dignified for our purpose. For starters, we've worked out a nice introductory chord-like yawn for which we haven't found or thought of any conventional way to begin to transcribe beyond pitches, durations, dynamics and ligatures.
As enthusiasts without formal schooling, we're making do with “sonnolento sostenuto” for the tempo / mood and “alla yawn” for the intro.