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Making Quantisation Work For You

Used effectively, quantisation can do much more for your sequenced music than simply cleaning up a sloppy playing technique. Craig Anderton supplies some helpful guidelines...


Used effectively, quantisation can do much more for your sequenced music than simply cleaning up a sloppy playing technique. Craig Anderton supplies some helpful guidelines...

Just about every sequencer on the market allows you to quantise (also called 'auto-correct') tracks-to 'round off' notes to the nearest specified rhythmic value. For example, if you choose to quantise a track to eighth notes (quavers), then a note played slightly behind or ahead of the eighth note will be repositioned to land exactly on the eighth note (Figure 1). Most sequencers (and drum machines) let you specify a quantisation value, typically from quarter notes up to 32nd notes (some offer even finer resolution). Many sequencers add their own little touches that help make quantisation a creative tool, not just something that corrects timing problems.

Figure 1. How quantisation aids rhythmic accuracy.


But while quantisation can help clean up sloppy keyboard technique, it can also make your music sound mechanical. And you can run into problems if you quantise to the wrong value - for example, a part with 16th notes quantised to eighth notes will (in addition to altering the feel drastically) 'stick' notes together (Figure 2). Fortunately, almost all undesirable side effects can be avoided if you know how to use quantisation, as illustrated in the following tips.

Figure 2. Improper quantisation can sometimes 'stick' notes together.


IN SEARCH OF NON-DESTRUCTIVE QUANTISATION



With most sequencers, you record a part first then quantise it. But what if, on playback, you don't like the effects of quantisation, or you selected an inappropriate value? In many cases, the sequencer will let you easily recall the original track so that you can try again. However, this must be done before doing any recording or other activity that writes data into memory (playback is okay, though). Listen to a track all the way through after trying a particular quantisation value, since certain parts of the track might not work with the value necessary to clean up other parts of the track. Better yet, if the sequencer allows, restrict quantisation to only those measures or sections where you truly need quantisation.

Even if your sequencer permanently alters a track when quantising, you can still simulate non-destructive editing: simply copy the track to an open track and do all your experimenting on the copied track. If you blow matters totally, just erase the copied track, copy the original over, and try again.

My least favourite kind of sequencer forces you to decide how you're going to quantise a track before you start playing, and then corrects as you record; if you play a great part but the quantisation is wrong, you're stuck with the part. To solve this problem, record all your tracks with no quantisation (or the finest resolution possible). Then, to quantise a track, play it back over the sequencer's MIDI Out (mute all other tracks so that only the track to be quantised appears at the MIDI Out). Connect a MIDI lead from MIDI Out to MIDI In, set the sequencer to record on an open track, and select the desired amount of quantisation. The unquantised data at the MIDI Out goes through the lead back into the MIDI In, and becomes quantised during the recording process. If the quantisation doesn't work, erase the quantised/bounced track, choose a new value, and try again.



"Record your hands running up and down the keyboard a few times, play the track back through a MIDI drum machine, and experiment with different types of quantisation."


DEFAULT TIME



Those just discovering quantisation often wonder what value to choose when recording various sequenced parts. My initial quantisation preference for drum machines is 16th notes. Eighth notes don't allow for sufficiently complex patterns, and 32nd-note quantisation requires very accurate playing — if you're just a little bit off, you might find your beat placed on the wrong 32nd note.

Bass parts usually get eighth note quantisation, as do initial bass drum and snare parts if I'm overdubbing drum parts into a sequencer. Keyboard comping usually rates 16th notes, and MIDI guitar synth parts always start out with no auto-correction at all (see below).

MULTIPLE QUANTISATIONS ON A SINGLE TRACK



You can mix quantisation values on a single track if your sequencer can cut (erase) and paste (bounce) parts of tracks. For example, suppose you are recording a keyboard part that faithfully follows the rhythm up to a particular non-rhythmic verse, so you want to switch from quantised to real-time recording. To do this, record the keyboard part on Track A with quantisation turned off. Now bounce that track over to Track B. On Track A, cut out the non-rhythmic part, and on Track B, cut out everything except the non-rhythmic part. Now quantise Track A as desired, but leave Track B alone. Then bounce Track B and Track A together, and hey presto - a single track with both quantised and unquantised sections. This technique is particularly useful when you need to integrate triplets into a non-triplet-oriented track.

QUANTISING MIDI GUITAR SYNTH PARTS



Proficiency in the art of cutting and pasting, as well as bouncing, is vital when quantising MIDI guitar parts. Strumming the strings produces effects that just don't happen with typical keyboard playing; but if you quantise MIDI guitar parts, you lose that magic since all the notes of a chord come crashing down at the same time. I generally bounce individual sections of an unquantised guitar sequence that need to be quantised over to another track (note that sections of this new track may be as short as a measure or two), cut the part from the original track, quantise the new track in one pass, then bounce the two tracks back together again.

In many cases, though, if your playing is 'close enough' it's best to forget about quantisation, and simply edit individual notes that don't fall where you want them (assuming that your sequencer supports individual note editing).



"Many sequencers add their own little touches that help make quantisation a creative tool, not just something that corrects timing problems."


FLAVOURS OF QUANTISATION



Not all sequencers quantise in the same manner. Some quantise just the attack of a note (ie. where it begins); others also quantise the note duration. Some devices let you perform one, the other, or both - definitely the most flexible way to go. I find attack quantisation most useful; quantising duration often sounds unnatural (not always a bad thing, of course).

BEYOND QUANTISATION



Now that you've quantised your track, it's time for some individual note editing to produce a better feel. Adding subtle variations can greatly improve the feel of a track. Go ahead, slide that snare hit a few milliseconds ahead of or behind the beat, or 'strum' the notes of a piano chord by starting the note attacks at slightly different times.

Advanced sequencers will even let you do tricks, such as quantise only those notes that fall outside an acceptable range of quantisation (for example, if you specify a ten-clock pulse 'window' around a particular beat, then events that occur more than ten clock pulses away from the beat will be quantised, but events within ten clock pulses of the beat will remain as recorded). This helps you keep a good 'feel' and still trap the most significant timing errors. Some sequencers let you delay or advance tracks, or quantise only notes within certain pitch ranges. Adjusting these parameters can really add a new dimension to a part.

Quantisation can also work for you as a compositional aid. What would that part sound like quantised to triplets? It's easy to find out. Looking for a random rhythm pattern to give you some ideas for unusual rhythmic grooves? You don't necessarily need a brand new piece of computer software - simply record your hands running up and down the keyboard a few times, play the track back through a MIDI drum machine, and experiment with different types of quantisation. You can even try bouncing that track twice - quantised once to triplets and once to, say, 16th notes. The polyrhythmic interplay can be very inspirational.

These are just some ideas. Find out what your sequencer can do, and experiment. Proper use of quantisation can make the difference between a great-sounding sequence and one that's just average.

© 1987 Mix Publications Inc. Reproduced with the kind permission of the publishers.



Previous Article in this issue

Using the Alesis HR16 as an Expander

Next article in this issue

Trackman Sequencer


Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.

 

Sound On Sound - Nov 1988

Donated & scanned by: Mike Gorman

Topic:

Sequencing


Feature by Craig Anderton

Previous article in this issue:

> Using the Alesis HR16 as an ...

Next article in this issue:

> Trackman Sequencer


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