For his NYU music technology masters thesis, Tyler Bisson created a web app called Groove Pizzeria, a polyrhythmic/polymetric extension of the Groove Pizza. Click the image to try it for yourself.
Groove Pizzeria
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Note that the Groove Pizzeria is still a prototype, and it doesn’t yet have the full feature set that the Groove Pizza does. As of this writing, there are no presets, no saving, no exporting of audio or MIDI, and no changing drum kits. You can record the Groove Pizzeria’s output using Audio Hijack, however.
Like the Groove Pizza, the Groove Pizzeria is based on the idea of the rhythm necklace, a circular representation of musical rhythm. The Groove Pizza is a set of three concentric rhythm necklaces, each of which controls one drum sound, e.g. kick, snare and hi-hat. The Groove Pizzeria gives you two sets of concentric rhythm necklaces, each of which can have its own time duration and subdivisions. This means that you can use the Groove Pizzeria to make polyrhythm and polymeter.
The words “polyrhythm” and “polymeter” are frequently used interchangeably, but they are not the same thing. Tyler’s thesis contains the clearest definition of the terms that I know of, which I paraphrase here.
- Polyrhythm is two or more concurrent loops of equal duration. Each loop consists of a set of evenly-spaced subdivisions or rhythmic onsets. The loops contain different numbers of onsets, meaning that the subdivisions of each loop are not same length. Finally, the ratio of the number of onsets in each loop is not a whole number (otherwise one loop would just be an even subdivision of the other). When people talk about 4:3 or 5:2 polyrhythm, this is what they mean. In Western music, polyrhythms usually only occur for short time spans in the form of tuplets, but in West African drumming, polyrhythms are a core structural feature.
- Polymeter is two or more concurrent loops of different duration. The onsets in each loop have the same duration, but each loop has a different number of onsets. This is much more common in Western music than polyrhythm. In Western music, you mostly see polymeter over short time spans in the form of hemiola or syncopation.
With these two definitions in mind, let’s take a look at the Groove Pizzeria interface. For each loop, you can control both the number of subdivisions (the number of onsets) in each loop and the length (duration) of each subdivision. The basic time unit in the Groove Pizzeria is one sixteenth note. Each of the “teeth” on the outer radius of each circle represents the duration of one sixteenth note. If you change the Time Units setting, you make the sixteenth notes shorter, and the radius of the circle gets smaller to preserve the cumulative distances between each tooth of the loop. The easiest way to understand the difference is just to draw some rhythm patterns on the grid, play with the sliders, and see what happens. Notice that the Groove Pizzeria visualizes the compound pattern formed by the two loops in the top left corner of the screen.
Here’s a 5:4 polyrhythm created by taking two loops that are the same length and dividing them into five and four steps respectively:
If you want a 5:4 polymeter rather than a polyrhythm, then you will need to adjust the number of time units in each loop as well. (The patterns aren’t perfectly symmetric so you can hear where they start and end.)
Here’s a less exotic sound, a 4:3 polymeter, also known as hemiola. On the left is a 4/4 hip-hop pattern. On the right, I made a 12-beat-long pattern that repeats four times in the same amount of time as it takes the hip-hip pattern to repeat three times.
Here’s a less familiar sound, an 11:5 polyrhythm. On the left, I made the closest thing to a hip-hop pattern that’s possible in 11/8 time, and on the right I made a simple quintuplet pattern. This will probably sound weird to you at first, but if you listen to it for a while, it will eventually start to make a wonky kind of sense.
How about some real-world examples? Genuine polyrhythm is unusual in popular music, but it’s not unheard of. James Blake uses a quintuplet hi-hat pattern in his song “Unluck.”
Here’s my Groove Pizzeria representation of this beat. On the left is the kick and snare playing a straight quarter note pattern in 4/4, and on the right is the hi-hat pattern (though it’s not playing back on a hi-hat sound.)
Hip-hop producers sometimes use polyrhythms to create specific varieties of swing. On drum machines, swing (sometimes called shuffle) shortens and lengthens each alternate beat. At zero swing, also known as 1:1 swing, the beats within each pair are the same length. At maximum swing, the first beat in each pair will be twice as long as the second beat in the pair. This is known as 2:1 swing, sometimes called “triplet swing” because it’s as if the first beat is two triplets long, while the second is one triplet long. In real life, you usually want your swing setting somewhere between these two extremes. (Click here for a more detailed explanation of swing.)
One way to get a swing ratio in between 1:1 and 2:1 is to use a quintuplet grid. If you think of the first three quintuplets in each group as being one “beat” in a pair and the last two as being the “beat” in the pair, you get the equivalent of 5:3 swing. Slynk explains how to set this up in Ableton:
Here’s a neo soul groove I made using pentuplet swing:
For an even narrower swing ratio, you can use septuplet swing. It’s the same idea, except now you’re grouping together the first four septuplets into one “beat” in the pair, and the last three septuplets into the other “beat”. This gives you a 4:3 swing ratio. This is pretty close to no swing at all, but it’s noticeably “off,” in a way that gives you a nice J Dilla “drunken drummer” feel. Slynk explains again:
Here’s a neo soul groove I made using septuplet swing:
Beyond complex rhythms, the Groove Pizzeria can teach another useful musical concept called event fusion. When a rhythm gets fast enough, you stop hearing individual beats and start to hear a continuous thrum. The transition happens at around twenty beats per second. If you play the rhythm even faster, the thrum becomes a steady pitch, and the higher the tempo, the faster the pitch. Here’s how you can experiment with event fusion yourself. First, put a clap on every sixteenth note. Next, reduce the number of time units to a small number (5 is fine) and set the tempo to 300 bpm. Now reduce the number of steps. Listen for the point when the claps fuse into a single tone. You can control the pitch of this tone by changing the number of steps.
If you think of more interesting music learning or creation applications for the Groove Pizzeria, please let me know. Happy drumming!