On-beat and Off-beat
In music that progresses regularly in 4/4 time, counted as "1 2 3 4, 1 2 3 4...", the first beat of the bar (down-beat) is usually the strongest accent in the melody and the likeliest place for a chord change, the third is the next strongest: these are "on" beats. The second and fourth are weaker - the "off-beats". Subdivisions (like eighth notes) that fall between the pulse beats are even weaker and these, if used frequently in a rhythm, can also make it "off-beat". The effect can be easily simulated by evenly and repeatedly counting to four: Bold denotes a stressed beat. As a background against which to compare these various rhythms a bass drum strike on the downbeat and a constant eighth note subdivision on ride cymbal have been added, which would be counted as follows:
- 1 2 3 4 1 2 3 4 -- play eighth notes and bass drum alone
- 1 2 3 4 1 2 3 4—the stress here on the "on" beat play But one may syncopate that pattern and alternately stress the odd and even beats, respectively, creating syncopation:
- 1 2 3 4 1 2 3 4 -- the stress is on the "unexpected" or syncopated beat play
So Off-beat is a musical term commonly applied to syncopation that emphasizes the weak even beats of a bar, as opposed to the "normal" on-beat. This is a fundamental technique of African polyrhythm that transferred to popular western music. According to Grove Music, the “Offbeat” is where the downbeat is replaced by a rest or is tied over from the preceding bar". The downbeat can never be the off-beat because it is the strongest beat in 4/4 time. Certain genres in particular tend to emphasize the off-beat. This emphasis is a defining characteristic of rock'n'roll and Ska music.
Read more about this topic: Backbeat