Rhythm was a bay horse bred in Kentucky by his owner Ogden Mills Phipps.
He was sired by Mr. Prospector out of the Grade I winning mare Dance Number who was a daughter of Northern Dancer.
An increasingly difficult temperament combined with a throat problem that necessitated surgery resulted in the colt's handlers having to skip the U.S.
In 2000, Rhythm was sent to Diamond F Ranch in Grass Valley, California where on September 4, 2007 he is reported to have fractured a leg in a paddock accident and had to be euthanized.
His most successful progeny were in New Zealand and Australia where he was the sire of three Southern Hemisphere champions including the outstanding filly Ethereal whose four Group One wins included three of the most important staying races in Australian racing: the Caulfield Cup, the Melbourne Cup and The BMW Stakes.