Polyrythms?

bass87 · #1 03-29-2003, 12:02 PM

I've heard these mentioned around these boards, but I'm not sure exactly what they are. I can guess from the name that it means more than one rhythm, but could someone please explain it fully to me? Any recommended listenings for them would be great too.

I did do a search, but it didn't come up with any clear explanations

Thanks for any help.

theautarch · #2 03-31-2003, 02:41 PM

my bass teacher went over this briefly with me a many months ago,....so i'm not completely sure myself. but i'll give it a shot.... he had me write some out and we played them together. one bassline was pretty basic with holes left in the line. the other bassline filled in those holes and complimented some notes from the first bassline. however, the two lines should be heard and felt as different rhythms.

I hope this helps out a little bit...i'm gonna ask my teacher again on friday to give me a quick explanation...i'll post it if nobody comes up with anything...we also played a song that was polyrhythmic, so i'll ask him what it was we played and post that as well.....

geshel · #3 03-31-2003, 07:03 PM

A polyrhythm generally is when two parts divide the measure into a different number of beats - usually where one is not a multiple of the other. For instance, one part plays three beats per measure (playing triplets, for instance), the other four. This creates a specific pattern, a new rhythm of its own.

Polyrhythm describes when the measure length is common between the parts - the next measure starts at the same time for each of them. So in a five against four polyrhythm, the beginnings of the "four" and the "five" part always line up.

Polymeter is slightly different. In this case, the underlying pulse is the same (all playing 8th notes, for instance), but the # of beats between pattern repeats is different between the two parts. So in a five against four polymeter, the "five" pattern is played four times, and the "four" pattern played five times, before they start at the same time again.

Polyrhythms show up quite often, at least partially, in music. Two v. three is all over the place, 3 v. 4 fairly common. Just using triplets or dotted notes against straight notes will bring this into play.

Polymeter is less common, though not obscure. King Crimson and Tool use it quite a bit - KC base whole pieces on the principle (Discipline for example); with Tool it shows up a lot with the drummer's use of accents. Soundgarden has too (My Wave for instance - the bass and guitar play in different time signatures for part).

geshel · #4 04-02-2003, 02:34 AM

Polyrhtyhm:

Two patterns of 4 v 3, two patterns of 3 v. 2, two patterns of 5 v. 4

http://home.attbi.com/~taylorsherman/polyrhythm.mid

geshel · #5 04-02-2003, 02:36 AM

Polymeter:

(lifted from the Trey Gunn piece "Kuma")

7/16 ostinato over a 4/4 bass line

http://home.attbi.com/~taylorsherman/polymeter.mid

geshel · #6 04-02-2003, 02:38 AM

One thing to keep in mind, is that the difference between polyrhythm and polymeter is really just a matter of scale. If you "zoom out", and look at the measure lines, polymeter looks like polyrhythm. For instance, the measure lines of a 5 v. 4 polymeter make up the same pattern as a 4 v. 5 polyrhthm.

Gad I'm tired of typing polyrhythm.

geshel · #7 04-02-2003, 02:42 AM

Final exam: tell me what's going on in this one:

http://home.attbi.com/~taylorsherman/ratios.mid

Three-part polyrhythms, based on the harmonic ratios which make up the chords in each bar. Though I think I had to cheat in a couple places.

edit: hmm, WMP doesn't pick up the tempo changes between measures when it plays it, but Jazz does. Oh well.

edit: fixed link typo

Howard K · #8 04-02-2003, 08:02 AM

well that just about blew my mind for the foreseeable future!

I saw an instructional drum video of Mark Mondesir where he played what you would describe above as a polymeter (although he referred to it as a polyrhythm).. he basically played 4 different meters - one with each limb. Insane. Utterly utterly insane.

There was another post on here about this kinda thing...
Peter McFerrin was talking abot one of his bands tracks that has a section of two bars of 7/8 and one of 8/8 while the melody is in 11/4 over the top... a total of 22 beats.

Interesting stuff... for real odd meters I guess a fantastic internal clock is needed!

Howard K · #9 04-02-2003, 08:03 AM

Quote:

Three-part polyrhythms, based on the harmonic ratios which make up the chords in each bar.

..so what is a harmonic ratio?!

ChenNuts44 · #10 04-02-2003, 08:08 AM

I listened to those midis...first thing that came to mind with striking similarity:

OLD SCHOOL VIDEO GAME MUSIC

I'm talking sega/nintendo days here. I couldn't name the games for you, but I can hum all of the lines...

Anyway, I'm quite sure that many contain some example of polyrhythms and polymeter.

bass87 · #11 04-02-2003, 01:34 PM

Thanks so much Geshel, that's a great help, if a bit confusing for a bass brain of my size

The sound clips were very useful too

Quote:

Originally posted by geshel

Polymeter is less common, though not obscure. King Crimson and Tool use it quite a bit - KC base whole pieces on the principle (Discipline for example);

I have that on CD somewhere so I'll have to dig it out and listen to it closely. Thanks again

geshel · #12 04-02-2003, 05:32 PM

Quote:

Originally posted by Howard K

..so what is a harmonic ratio?!

(note, the link was broken before, it should be fixed now)

The ratio in pitch between the notes in the harmony. In "just" intonation, the ratios in pitch from the R-3-5 in a major chord are 4:5:6

So, a just-intoned A major chord has 440Hz, 550Hz, and 660Hz pitches (not accounting for overtones, of course).

Of course, these days everthing is equal-tempered, so it's not quite that exact. The ratio of a major third is one of the most "off" so instead of 1.2 : 1 it's more like 1.26 : 1. But I based the stuff in this little ditty on what the "perfect" ratios would be anyway.

Howard K · #13 04-03-2003, 01:25 AM

Aah OK gotcha...

do you mind if I ask why you would choose to create music this way... not on an equal tempered basis?
i mean, sure that just makes it harder to play - especially in a group - and probably doesnt sound much different - does it sound very diffent?

I'm interested!

moley · #14 04-03-2003, 02:04 AM

With equal temperament, it's simpler - a semitone is constant - and it's the 12th root of 2 (i.e. 2 to the power 1/12), which is about 1.0595. This means, to find the note a semitone higher, you multiply by that number.

So, A = 440, therefore Bb = 440 x 1.0595 = 446.18

That's a slightly rough calculation, as I rounded down the 12th root of 2 - but you get the idea.

Howard K · #15 04-03-2003, 02:14 AM

Yeah, I understand.. but does it sound differnt if you dont have perfect pitch or an equal tempered reference?

I mean, by playing 'just tempered' is one just making things unneccessarily hard for oneself, with no noticable gain... or does everything sound strangely clearer or something?!!

moley · #16 04-03-2003, 02:25 AM

I don't know about clearer, but it sounds different, I think. Not that I've ever heard a piece of music played using the just tempered system, but I've heard what a major chord sounds like... it's sorta odd.

You don't get the "beat frequencies" with 3rds, like you do with the equal tempered scale. A major chord sounds sorta "perfect", but to the ear that's used to the equal tempered scale it sounds unusual. We're used to hearing the "beat frequencies".

And using the just tempered system, the further you get from the key it's appropriated to, the more out of tune it sounds.

geshel · #17 04-03-2003, 02:30 AM

What Moley said. And I should note, the tones in that MIDI file are equal-tempered. Playing in just intonation isn't something I'm really capable of. First, it's impossible on an equal-tempered fretted instrument. And my fretless intonation isn't that hot.

Playing anything other than one single major key in a just- or similar intonation gets very complicated very quickly.

I'll maybe record a sound sample of the difference between equal-tempered and perfect major thirds. I never noticed the dissonance in the former until I got my Hanewinckel - go figure.

Howard K · #18 04-03-2003, 02:37 AM

Quote:

never noticed the dissonance in the former until I got my Hanewinckel - go figure.

well i had a fretless for about 6 months - a 1980 ibanez musician - i sold it eventually as it was unlined (not an ideal learner instrument!) it also had areally muddy tone that i just didnt really get into...

anyway - i found that min 3rds did indeed sound weird and i could never quite intonate them properly - they just never sounded quite right somehow. i was so sure it wasnt my intonation as i sat there with a tuner many times to make sure i was 'dead on' and it still sounded odd. then i learnt about this equal temprement thingy and i think that had something to do with it somehow?

geshel · #19 04-03-2003, 02:47 AM

OK, here's an example. With the MP3 compression it's harder to tell, but we'll see.

This recording is a "set-up": I play (as close as I can) the perfect third first (two times), then the equal-tempered third after that (three times).

I checked the pitch of both notes with my tuner (on the V-Bass). The equal-tempered samples are just the notes fretted as is. To get the just-intoned version, I bent the low string up a bit (equal-tempered thirds are too sharp).

See if you can hear a difference. And if you can, how does it sound?

Bruce Lindfield · #20 04-03-2003, 02:48 AM

Quote:

Originally posted by moley
I don't know about clearer, but it sounds different, I think. Not that I've ever heard a piece of music played using the just tempered system,

I think you probably have - so Japanese classical music is based on this and you hear it as background to films/documentaries a lot, as a "clue" that we are in an oriental setting.

Also, if you have ever seen "Kabuki" theatre or No Plays on TV about Japan.

Kotos, shamisens,shakahuchis etc - try this link :

http://www.japan-guide.com/e/e2113.html

And using the just tempered system, the further you get from the key it's appropriated to, the more out of tune it sounds.

Japanese classical music now sounds so out of tune to the Japanese, that they don't listen to it much now!