Round robin sampling
In the previous pages we’ve already discussed how the multisampling process can be used to capture human variations in pitch, dynamics and articulations. Our example multisampled patch will play back different samples at different MIDI pitches and velocities, but playing repeated notes at the same velocity level will still play back the same sample over and over. A human performer or drummer will never play a note the same way twice, and so a technique called ‘round robin’ sampling is used to replicate this variation.
XLN Audio’s Addictive Drums 2 is one of the leading drum ROMplers around, utilising state-of-the-art multisampling technology to realistically emulate the world’s most famous drum kits. We sat down with Lars Erlandsson, Product Manager and co-owner of XLN Audio, to find out the ins and outs of the round robin technique.
FM: What exactly is ‘round robin’ sampling, and why is it useful?
Lars: “The general concept is that you want to eliminate the ‘machine gun effect’ when you have consecutive hits at the same velocity. The human ear is sensitive, and if you repeat the same sample it sounds machine-like rather than natural. When a real drummer plays a few hits with the same strength, there are always tiny variations. By sampling each ‘strength’ several times we can capture those variations, and by using round robin or random algorithms in the sampler engine you make sure that the same sample is never played twice in a row.
“So how many samples are needed? If you have two samples, you end up with an A-B-A-B-A-B pattern which still sounds unnatural and predictable. So I would say three or four is the minimum, especially in the more important layers – say, snare at velocity 100-110, which is used extensively.”
How does Addictive Drums 2 incorporate round robin sampling and other multisampling techniques? How many samples are used per sound/key/velocity range for instance?
“AD2 uses multiple velocity layers and ‘Alternating Samples’ (as we call it). The number of layers depends on the sound. Some sounds change timbre a lot between soft and hard hits, and to capture that you need more layers. Snare is usually 16 layers, Kick is 12. There are usually about four to eight alternating samples in each layer. The exception here is intentional ‘one-shot’ or drum machine-type sounds, where there might be only a single sample. AD2 also lets you control how many velocity layers you want to use, and if you want Alternating Samples on or off – because sometimes you want that expensive snare to sound like a vintage drum machine!”
Do you have any advice for readers who are creating their own round robin patches?
“Record a ‘ramp’ from soft to hard, and always record more hits than you think you’ll need. Then you can slice and dice afterwards – for example, eight layers with four alternating, or five layers with six alternating. If you have a lot of recorded hits sorted by strength, any consecutive hits will be similar enough that they can be used as alternating samples in the same layer (possibly with some tiny volume compensation).”
Is there a right or wrong way for a round robin patch to cycle through its composite samples? Should this be set up in a structured way, or should it be random?
“Either way works I think, as long as you have three or more samples. The only rule is that the same sample should never play twice in a row!”
Creative round robin sampling
While round robin sampling is predominantly used to emulate realistic instruments, you can misuse and abuse the feature for more experimental gains. Here’s one way to do it: chop up a vocal phrase into syllables, then load them onto the same keyzone in a sampler. Activate round robin sampling, then repeated presses of the assigned MIDI key will cause the sampler to cycle through these vocal segments.