Syncopation

Every metre has an expected pattern of strong and weak beats. In 4/4 it is strong, weak, medium, weak. Syncopation is deliberately putting emphasis somewhere else.

It is the reason a rhythm can feel like it pushes or pulls rather than marching.

Three ways to create it

Accent a weak beat. In 4/4, stressing beats two and four instead of one and three. This is the backbeat, and it underpins most rock and pop.

Play on the offbeat. Placing notes on the "and" between beats rather than on the beats themselves. Ska and reggae guitar do this almost exclusively.

Tie across a strong beat. Start a note just before beat three and hold through it. The beat arrives with no new attack, so the ear feels the emphasis displaced. This is the most common written form — see ties.

It depends on the pulse being clear

Syncopation is a contradiction, and a contradiction needs something to contradict. If the listener cannot feel where the beat is, off-beat notes do not sound syncopated — they just sound random.

This has a practical consequence for practice: you cannot play syncopation convincingly without an internal pulse. Playing a syncopated figure without counting produces something that sounds vaguely wrong in a way that is hard to diagnose.

The fix is unglamorous. Count the subdivision out loud — "one and two and three and four and" — and place the notes against it. Slowly. Then with a metronome on beats two and four only, which forces you to keep the pulse yourself.

Where it shows up

Syncopation is not a modern invention. It appears in medieval and Renaissance music, throughout Bach, and all over the classical repertoire. What changed in the twentieth century is that it moved from being an occasional effect to being the default: jazz, blues, funk, rock, Latin and hip-hop are all built on it.