Rx for REX

But a less obvious application is using the samples to create drum loops from scratch — and you don’t even need great timing, as you can drag-and-drop them into the host. What’s more, it’s possible to create loops that stretch perfectly with tempo, sounding virtually the same at 50 bpm as they do at 150 bpm. Don’t believe me? Keep reading.

LOOP CREATION FROM HITS: STEP-BY-STEP

1. Create a sequence (also called project, song, etc.), and set the tempo to that of your project. If you’re not working on a particular project and just want to create some loops, use a “generic” base tempo (e.g., 80 for rap, 120 for house, 133.33 for “locked groove” dance, 140 for techno, 160 for drum ’n’ bass, etc.).
2. Set up a rhythmic reference (e.g., a sixteenth-note grid) in your host program and enable its snap-to-grid feature. To humanize the track later, turn off the grid and move hits around to create more interesting timings.
3. Collect the drum samples for your loop in a folder.
4. Import and place your samples. I devote a separate track to each particular sound, although sometimes it’s helpful to distribute the same sound on different tracks if specific sounds need to be processed together. For example, Figure 1 shows a techno loop with a sixteenth-note hi-hat part spread across tracks 1–4. As I wanted to accent the hi-hat hits that fall on each quarter note, these go on their own track, as do the hits falling at the beginning of a measure. The open hi-hat part also goes on its own track. This makes it easy to adjust the relative levels of the four sets of hits, creating a more dynamic hi-hat part.
5. Bounce and save. Once you have a great loop, bounce all the tracks together into a mono or stereo WAV or AIFF file (typically using the host’s bounce or export function). Also consider making a mono or stereo mix of each drum sound, as well as special-purpose mixes (e.g., all sounds except kick). You can then save these different mixes in a single folder for that particular loop.

STAY FLEXIBLE!

Giving each sound its own file allows lots of flexibility when creating variation loops. Here are a few examples.

• Slide a track ahead of or behind “the pocket” for different feels.
• Use pitch stretching (while maintaining duration) to create timbral variations.
• Drop out individual tracks to create remix variations. 
• With a percussion track that’s more accent-oriented (e.g., tambourines, shakers, etc.), and assuming your host allows loops of different durations on different tracks, truncate an eighth-note or quarter-note from the beginning. Because the loop duration will be shorter than the main loop, it repeats a little sooner each time the main loop goes around, thus adding variations.
• Pitch-shift a track down an octave to fatten up the sound. This works especially well when layered with the unprocessed track. 
• Copy, offset, and change track levels to create echo effects. Eighth and sixteenth-note echoes work well, but try dotted and triplet values as well.

PERFECT STRETCHING

If you save the original sequence, you can always change the tempo later, then generate loops at different tempos. This is because each hit will be anchored to a particular place in the timeline. For example, if a snare sound hits at beat 2 of measure 3, it will always hit there (regardless of the tempo) because the sample start is associated with a particular musical time in bars, beats, and measures. This is similar in principle to how files work that follow the REX file standard from Propellerheads.

JARGON JOCKEY

• REX Files: REX format loop files, developed by Propellerheads, work similarly to the procedure described in this column — but in reverse. Instead of constructing a loop from individual hits, Propellerheads’ ReCycle program for creating REX files de-constructs an existing audio loop into individual hits. MIDI notes placed on the timeline trigger these hits. Because the notes are anchored to a specific musical position in the timeline (e.g., 4 measures, 2 beats), the note triggers the audio sample at the correct musical time, regardless of tempo.