Double whole note either of two ways: by a hollow oval note head, like a whole note, with one or two vertical lines on either side, as on the left of the image, or as the rectangular shape also found in older notation, shown in the middle of the image (; ). Because it lasts longer than a bar in most modern time signatures in common use, the breve is rarely encountered except in English music, where the half-note is often used as the beat unit . A related symbol is the double whole rest (double rest or breve rest), which usually denotes
Sixty-fourth note twenty-eighth note—otherwise known as the "semihemidemisemiquaver" —and even shorter notes, are occasionally found. Sixty-fourth note In music notation, a sixty-fourth note (American), or hemidemisemiquaver or semidemisemiquaver (British), sometimes called a half-thirty-second note , is a note played for half the duration of a thirty-second note (or demisemiquaver), hence the name. It first occurs in the late 17th century and, apart from rare occurrences of hundred twenty-eighth notes (semihemidemisemiquavers) and two hundred fifty-sixth notes (demisemihemidemisemiquavers), it is the shortest value found in musical notation . Sixty-fourth notes are notated with a filled-in oval note head and a straight note stem with