# Why are Round Robins needed?



## moonunit (Apr 18, 2012)

Hello there,
I'm trying to get my head around round robins and even trying to understand why they are needed.
Am I correct in thinking Round Robins are used to eliminate the weird phase sound if a sample is triggered if it is already playing?
If this is the case and you have say 6 groups that all use the same samples and all groups are cycling in a RR,would it not be playing the same samples anyway?
Or do you have to alter sample start points for each group.It has me baffled as to what it is achieving using a RR.
Am I totally missing the point?
Thanks guys.
Fabian.


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## andreasOL (Apr 18, 2012)

> Hello there,
> I'm trying to get my head around round robins and even trying to understand why they are needed.
> Am I correct in thinking Round Robins are used to eliminate the weird phase sound if a sample is triggered if it is already playing?



Well, that _could_ be a use for round robins, but in most, if not all, cases they are use to avoid the so-called "machine gun effect" that you brain signals, if you play a note repeatedly.



> If this is the case and you have say 6 groups that all use the same samples and all groups are cycling in a RR,would it not be playing the same samples anyway?



Hmmm...yes, but what you describe is no round robin. To have six round robin groups you have to record the acoustical event six times. These then are (should be) sufficiently uncorrelated phase-wise so that no phase issues arise.

What you describe happens if you use the same patch e.g. on multiple tracks and play the same note more than once. Then you get either phase issues (comb filter effect) or, if you trigger the same note at the same time, merely an increased volume of one note.

So you cannot build an ensemble from solo instruments by re-useing the patch. You have to either record the solo instrument multiple time or use pitched neighbour samples (some Kontakt instruments offer this (by scripting)).



> Or do you have to alter sample start points for each group.It has me baffled as to what it is achieving using a RR.



This would probably lead to comb filtering if you are not altering the sample start point by a great amount (> 100ms) which probably would take away important parts of the attack.

best,
Andreas


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## moonunit (Apr 18, 2012)

Thanks for the reply-yeah I think your absolutely spot on.
I have just set up 3 groups and filled them with the sames samples,but started the start point of each group in a different place and it lead to a sort of comb filtering effect as you described.
I'm still not understanding why different recordings of the same instrument will not produce similar comb filtering effects.
Lets say I have a simple yamaha fb01(fm module) bass sound and I record it chromatically and place it in one group then I record it again and place it in a seperate group then again and place it in another group and then cycle through them-Will that not produce a similar combe filter effect because they are the same sound just different recordings?
Or does some weird law of physics come in to play?
 
Sorry for the dumb questions,I'm still not getting how another recording of the same instrument makes any difference.
Cheers,
Fabian.


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## Mike Greene (Apr 18, 2012)

Andreas covered everything really well.

One thing I'll add is that the clearest way to hear the "machine gun" effect is to play 1/16 notes on a snare drum from a library that does *not* have round robins. It will sound like . . . a machine gun! Yet if you play the same 1/16 notes using a library that _does_ have round robin samples, it will sound a million times better, even if the 1/16 notes are hard quantized.


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## Mike Greene (Apr 18, 2012)

moonunit @ Wed Apr 18 said:


> I'm still not understanding why different recordings of the same instrument will not produce similar comb filtering effects.
> Lets say I have a simple yamaha fb01(fm module) bass sound . . .


In that case, you probably will get comb filtering, since a digital synth is likely to produce identical waveforms with each note repetition. Round robins are probably (others may have more educated opinions than I do) not going to have much benefit with digital synth samples.

It's "live" instruments where round robins pay off, since each time a note is plucked (or bowed or sung or whatever,) there will be lots of differences in the waveform. Even analog synths will have _some_ variation.


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## moonunit (Apr 18, 2012)

Thanks for the answers guys.
So in effect Round Robins are used to stop the machine gun effect and work to stop phasing issues when playing samples of 'real' instruments because with 'real' instruments due to the human variation that is imposed on a recording when recording a 'real' instrument this stops phasing issues.
I have just tried it with an analogue string sound with a long release and it gets that weird comb filtering effect when I play the same note.
I need to try 3 different recordings of the same string sound to see what happens.
Cheers,
Fabian.


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## polypx (Apr 18, 2012)

Round Robins are generally needed on acoustic samples, not synth samples. 

Lets say you have a robot arm, and it plays the same snare over and over again at the exact same velocity. The sound will be different every time... this is the chaotic nature of instruments, turbulence, no matter how precise you are, the sound is different.

But if you play the same SAMPLE over and over again, it sounds very obviously fake (the "machine gun" effect). So sample developers use robins to rotate or randomly select from a group of ideally very similar samples to stop your ear from noticing the repetition.

Your ear is far more sensitive than you think. We are more easily tricked by our eyes than our ears...


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## Ed (Apr 19, 2012)

If you hit a drum or pluck a string it will not sound exactly the same each time you do that. So if you only have one sample *recording* triggering over and over this is very unrealistic. The more rr's the less likely it is that you will notice the same sound repeating, and therefore will appear to be more real.

edit, didnt read down the thread.


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## MacQ (Apr 19, 2012)

An important consideration is that it's often small variations in the harmonic content of the sound that will distinguish one recording from another. Even sounds that are almost indistinguishable from one another in a single-listen context will sell the illusion of "human" performance as long as the harmonic content is sufficiently different. And it's actually pretty incredible how SMALL these differences can be while still defeating the "machine-gun" effect. The fundamental frequency and even the first few harmonics can be identical, but high-frequency variation makes it sound like a different sample.

Currently my biggest pet-peeve is RR samples that AREN'T consistent. Like, radically different tone/volume/attack/etc. on different samples. Worse when it's only on one or two samples, because you can really hear it when the RR cycle starts again. I think in the desire to add "human" performance to a track, you can actually go to far. The difference between a top-level percussionist and a computer sequencer is REALLY small ... but people will often trend towards "bad-school-band" -- overshooting completely to achieve the kind of expression that they think makes it sound less "synthy", but is actually making their performances sound inconsistent and distractingly bad.

Lots of stuff can work WITHOUT round-robin. Arco strings, for example, can usually get away with no round-robin (unless you're doing repeated interval figures, which is what the "Adagio" product is designed to combat). For short articulations of just about anything, it's almost a necessity if you plan to trigger the same note in rapid succession. For SYNTH sounds, it's a waste of time. Unless you're altering each note sufficiently, you'll get the phasey comb-filtering sound.

~Stu


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## Ed (Apr 19, 2012)

When an rr jumps out at you its bad yes!

For synths its pointless because you can just have a random start offset which makes it sounds like like its slightly different each time


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## mk282 (Apr 20, 2012)

It's not exactly pointless for synths, especially if you're sampling analog synths.


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## Ed (Apr 20, 2012)

Depends how accurate a representation you want of course. Its just, with synths the possibilities are endless and "realism" doesnt really matter, but for an acoustic instrument it really does.


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## germancomponist (Apr 20, 2012)

Mike Greene @ Wed Apr 18 said:


> Andreas covered everything really well.
> 
> One thing I'll add is that the clearest way to hear the "machine gun" effect is to play 1/16 notes on a snare drum from a library that does *not* have round robins. It will sound like . . . a machine gun! Yet if you play the same 1/16 notes using a library that _does_ have round robin samples, it will sound a million times better, even if the 1/16 notes are hard quantized.



Yes, but with a little bit tricky programing one can get best results with only one sample. 

Listen to this snare drum, built with only one sample in Kontakt sampler (no scripting, only editing....):

https://www.box.com/s/99b1a3d2299c48067f7c

If you like to see what I did, feel free and download the snare instrument here: https://www.box.com/s/065844bc3507a3328fa8

o-[][]-o


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## moonunit (Apr 21, 2012)

Thanks guys,
lots of info to digest there 
I'm thinking of just having the RR to stop the machine gun effect you talk about.
Also because it is a collection of bass I want to sample I was thinking of maybe having some sort of mono thing going on to stop it being polyphonic so any new note will stop the old note from playing and therefore stop the weird comb filter effect.Not sure how to force Kontakt to 'kill' existing playing notes.It would be nice if Kontakt had some nice ksp command to do this.I see ksp has playnote,is there a stop note command?
Cheers.


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## moonunit (Apr 21, 2012)

Thanks Germancomponist,
just downloaded it and tried it out-Works great.It is using Kontakts RR system.I always wondered how to set one of those up in Kontakt.
Cheers.


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