Master Class: By the Slice

Jul 1, 2009 12:00 PM, By Len Sasso

           
 

CREATIVE WAYS TO MANIPULATE AUDIO WITH STEP SEQUENCERS AND ARPEGGIATORS

Get added mileage out of your library of sliced audio files by playing their slices using a step sequencer or arpeggiator. Either option is more interactive than triggering the slices from a MIDI file. And because audio file slicing is easily done in most DAWs and sample editors, you can adapt this process to any file in your arsenal.

Step sequencing and arpeggiation are, by their nature, grid-based; steps are timed to note divisions. Therefore, working with grid-sliced audio will most closely align the results with the original, but that's no reason to limit yourself to grid slicing. Event-sliced audio, in which each slice holds a complete audio event such as a note or short phrase, often makes equally good fodder. Here, I'll illustrate both approaches using the step sequencers, arpeggiators and sample players in a variety of software applications.

Within Reason

If you're a Propellerhead Reason 4 user, then you have all the tools for both step-sequencing and arpeggiating sliced audio, and you have a lot of REX files with which to work in the factory library. The Dr.REX Loop Player is the obvious first choice for playing REX files, although Reason sample players NN19, NN-XT and Redrum offer useful playback options. The RPG-8 arpeggiator and the Matrix step sequencer are the logical choices for slice triggering, but the step sequencers in Redrum and the Thor Polysonic Synthesizer are viable alternatives.

FIG. 1: This Matrix sequence of tied 16th notes plays the Dr.REX slices in their original order and eighth-note timing, while its Curve pattern (not shown) manipulates the Dr.REX filter cut-off.

In Dr.REX, slices are triggered in left-to-right order by notes ascending from C1, MIDI note number 36. Dr.REX does not have gate and CV inputs for triggering individual slices, so circumvent that by encasing it in a Combinator and using the Combinator's gate and CV inputs. To make use of those, ensure that Receive Notes is enabled for Dr.REX in the Combinator's Programmer and cable the trigger module's outputs to the Combinator's inputs. (The trigger module does not need to be inside the Combinator.)

Working with Matrix is similar to using a trigger file on a sequencer track — you manage the trigger notes in a piano roll-style display (see Fig. 1). You cannot freely move notes in time, but you can shift them by whatever Matrix resolution (aka, step size) you choose. To ensure that the full slice plays at each step, create tied gates in Matrix by setting their velocity bars while holding the Shift key. Note that the velocity settings on Dr.REX determine whether the velocity bar values have any effect. Tied gates also ensure that consecutive steps used for the same slice will not retrigger. You can activate the Matrix Shuffle button to apply the song's global shuffle to patterns, but bear in mind that in Reason, shuffle is always 16th-note based.

One advantage to using a Matrix is that it can store up to 32 patterns, and you can automate pattern changes on a sequencer track. If the Matrix is inside the Combinator, you might assign a Combinator knob to select the pattern and then assign a MIDI controller to that knob. Don't forget that each Matrix Note pattern has an associated Curve pattern, which you can use to modulate other Dr.REX parameters such as filter cut-off (see Web Clip 1).

A Chord Apart

The hookup for the RPG-8 arpeggiator with Dr.REX or Redrum is the same as for Matrix except that if RPG-8 is inside the Combinator, then you need to ensure that Receive Notes for the RPG-8 is disabled (unchecked) in the Programmer. Otherwise, notes played by RPG-8 will be fed back and will prevent it from working properly. You also need to have a sequencer track for RPG-8 to feed it notes.

Redrum presents an interesting alternative to Dr.REX because you can load individual slices from one or more REX files into its pads, and because the individual pad controls differ from each other and from the individual slice settings in Dr.REX. That lets you cull the slices that are best for sequencing or arpeggiating and allocate them to the pads with the most useful options. Furthermore, each pad has a pair of effects sends and an optional separate output, greatly expanding the processing possibilities.

RPG-8 offers all the standard arpeggiator features and a couple of helpful extras: some unusual arpeggiation insert modes and a pattern sequencer with up to 16 steps. Insert modes 3-1 and 4-2 modify the chosen arpeggiation pattern by jumping one or two steps back in the pattern for every three or four steps forward. You use the pattern sequencer to insert rests (not to silence steps) in the arpeggiation pattern.

In Web Clip 2, I loaded 10 slices from a 30-slice piano loop into Redrum's 10 pads. I used the individual pad controls to shorten each slice to make them staccato; retune some of them; balance their levels; pan odd-numbered pads left and even-numbered ones right; and send the odd- and even-numbered pads to reverb and delay effects, respectively. I then used 4-2 insert mode and a 14-step pattern to create variations on upward arpeggiation.

The RPG-8 also serves as a MIDI-to-CV converter, allowing you to route MIDI mod wheel, pitch bend, aftertouch, expression and breath controller messages to Reason-device CV inputs. You can route these directly to Redrum, Dr.REX and effects-processor inputs or to a Combinator's modulation inputs, which you would then route using the Combinator's Programmer.