While you probably know "by heart" the rhythms of a favorite song, you might seldom hear, much less memorize, your heart's own endless cadence. In sudden cardiac death — when the heart basically stops, often with little or no obvious warning — the dynamics of the heartbeat can be an important, though seemingly subtle, forewarning that things are amiss. By seeking out the genes that help control the pace of the heartbeat, scientists may now have new insights that could help to explain this insidious condition.