Pulses and pyramids
Traditionally, eighth-notes, 16th-notes and so on are thought to be subdivisions of the quarter-note – fragments of the main pulse that, when added together, form whole beats. This is an effective way to describe where the notes are, but it doesn’t say anything about the effect of those notes, and it certainly doesn’t give you any ideas about what you can do with them. Instead of the above explanation, try to think of things in a different way…
In another model of thinking, smaller note values can imply other pulses. Instead of just the quarter note-pulse, there are a host of harmonically-related pulses that work together to create a stronger groove. As pulses, there may be eighth-notes, triplets, 16th-notes, half notes, whole notes, dotted eighth-notes and more. Any harmonically-related pulse faster that the main pulse is a harmonic, while any harmonically-related pulse that is slower is called a subharmonic.
Each harmonic or subharmonic pulse is independent of the main pulse, and the pulses as a group only sound good together because they fit with each other. The same rules that govern the harmonic series in pitches seem to govern rhythm as well: the more closely related the pulses are, the more consonant they feel. Don’t just stick with the basics, though – adding some dissonance into your groove can give it a lot of depth and complexity and work to sync listeners’ brains much more effectively.
Lining up the timing
Each pulse has its own polarity, and while they often line up, they don’t have to. In reggae, for example, the quarter-note pulse starts on the upbeat, but the eighth-note pulse starts on the downbeat. You can also flip the polarity during the song – something called ‘turning the beat around.’ Ironically, Gloria Estefan’s 1994 hit Turn The Beat Around doesn’t actually turn the beat around; instead, it maintains the expected polarity for its intended American audience. The song is a disco song with Cuban flavour, not the other way around.
Incidentally, you can flip the polarity of an entire song, a part of a song, or even just for a couple of beats. This is a common device in songs, both as a fill and as part of the main loop. When a change of polarity is a regular feature of the groove, it is often either at the end of the loop or three quarters of the way through.
Remember, though: the polarity of the pulse isn’t defined by you, but by your listener. Someone who expects the pulse to start on the downbeat is likely to hear it that way, even if you don’t want them to.