sixty-fourth note

US /ˈsɪksti fɔːrθ noʊt/
UK /ˈsɪksti fɔːrθ noʊt/
"sixty-fourth note" picture
1.

a musical note with a duration of 1/64 of a whole note

:
The composer used a sixty-fourth note to create a very fast, fleeting sound.
Playing a series of sixty-fourth notes requires advanced technique.