Well actually, if we really want to get into academics, nobody here is correct about polyrhythm. (i cant view that clip on my phone btw) What steevio is saying about 7/8 against 4/4 is not a polyrhythm, it's polymetric.
The latter part of what I was on about was in reference to the meter or time sig. In which case, I was saying if I read the sig as being, 7/8, Id have problems feeling that rhythm for anything that is dance music. That's not to say I dont use polyrhythms, we all do but the use of the term is the confusion here.
Like I was saying though, I dont really use polymetric stuff, which is actually what steevio is describing. So in a nutshell:
Polyrhythms: I use them.
Polymetering: I do not.
So what's the difference? Well as far as I am aware, its this (but feel free to argue this)
Polymetering: The use of 2 or more time sigs being played simultaneously at the same bpm. Say I had a chord riff in 3/4 and a bass riff in 4/4, that is not a polyrhythm. Thats polymetric. The effect is that they would first appear to be in 'sync' but then would go out of sync against each other and would realign (in the above case) after the 12th beat.
Polyrhythm: 2 or more different rhythms played against each other in the same amount of space. I think theres some stressing of accents to truly be polyrhythmic but Im not sure on that to be honest. Anyway, the very fact that it has been written in this thread with a slash and not a colon, signifies a time signature and not a polyrhythm.
When referring to metering, we use a /. When talking about polyrhythm, we use a :
So to say a polyrhythm is a 7/8 played against a 4/4 is not actually correct as its polymetering, hence my follow up post which then talked of time signatures. So its worth ensuring we know what each other is actually on about beforehand. Ive heard steevios music and know what hes on about when he talks about it even if the terminology might be misunderstood.
So in terms of say 7 notes per beat (septuplets) if we played septuplets against quarter notes in a 4/4 measure, that's a polyrhythm and would be written as a 7:4 polyrhythm. At least thats my grasp on it.