If you remember that the P wave indirectly produces the S4 and the QRS is indirectly responsible for the S1; then, if you know that the S2 occurs at the end of the T, the rhythm of S4, S1, and S2 is the same as that of P, QRS, and the end of T.
Because the P is closer to the QRS than the QRS is to the end of the T, the rhythm or cadence of an S4 gallop is a pair of sounds close together followed by a pause, then the second sound. Therefore, the rhythm of two cycles would be as follows 4-1-2-4-1-2.
Vocal imitations of the heart sounds can help in perceiving the actual phenomena.
Because the S4 is low-pitched, you should practice imitating the S4-S1-S2 by saying "huh-one-two." Place the "huh" as closely as possible to the "one," so that they are practically one word: "huh-one." Also, say the "huh" as softly as possible, because the S4 is often just within the realm of audibility. Like the S3, it is also volume- and proximity-dependent so that it tends to range in and out of audibility from beat to beat when it is soft.
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