trill

a note that alternates rapidly with another note a semitone above it

the articulation of a consonant (especially the consonant `r') with a rapid flutter of the tongue against the palate or uvula; "he pronounced his R's with a distinct trill"

pronounce with a trill, of the phoneme `r'; "Some speakers trill their r's"

sing or play with trills, alternating with the half note above or below