Jamieson, Fausset and Brown on Exodus 15:20

20. Miriam the prophetess--so called from her receiving divine revelations (Nu 12:1; Mi 6:4), but in this instance principally from her being eminently skilled in music, and in this sense the word "prophecy" is sometimes used in Scripture (1Ch 25:1; 1Co 11:5).

took a timbrel--or "tabret"--a musical instrument in the form of a hoop, edged round with rings or pieces of brass to make a jingling noise and covered over with tightened parchment like a drum. It was beat with the fingers, and corresponds to our tambourine.

all the women went out after her with timbrels and with dances--We shall understand this by attending to the modern customs of the East, where the dance--a slow, grave, and solemn gesture, generally accompanied with singing and the sound of the timbrel, is still led by the principal female of the company, the rest imitating her movements and repeating the words of the song as they drop from her lips.