Objective: Time-stretch loops not by using “Acidized” DSP techniques, but by cutting them into slices and playing them back based on their position in a sequence.
Background: Sonar can read and edit “Acidized” files that follow tempo automatically. However, using DSP to create these changes can introduce audible artifacts. With highly percussive loops such as drums, an approach like that of Propellerheads’ ReCycle — which cuts a file into pieces, then triggers each piece sequentially — may provide higher fidelity (if the triggers move closer together, the tempo speeds up; if they move further apart, it slows down). In Sonar, cutting a loop into smaller clips can accomplish the same end result without having to explicitly trigger each clip; here’s how.
Step by Step: You can usually proceed through each step in sequence. But if the file isn’t sliced finely enough, repeat steps 4 and 5 until you isolate each hit in the loop.
1. Drag the file you want to loop into Sonar. Or, double-click on a loop in the Loop Explorer view to place it in a track. (If it’s a “groove clip,” turn looping off: Click on the loop when it’s in Sonar, and type Ctrl-L.)
2. For the finest resolution when trimming (next step), turn on Snap to Grid. Specify snapping to an Absolute Time of 0 samples, with Snap to Audio Zero Crossings off, and mode set to Move To.
3. Set Sonar’s tempo to the loop’s original tempo (important!), then fine-tune the tempo and/or trim the loop so the loop end falls exactly on the beat. If you shorten the length while trimming, go Edit > Apply Trimming.
4. Select the Scissors tool then cut at each major loop transient, as close to the exact transient beginning as possible.
5. If you hear clicks with some slices, add very short fades at the slice ends (or possibly beginnings) as needed.
6. Done! At slower tempos (shown), each beat takes longer so slices play back further apart. At faster tempos, they move closer together.
Tips How good is the stretch quality? Judge for yourself , hear the original 133.33 BPM file, then stretched down to 110 and up to 160 BPM. When sped up, you will likely need to shorten the final slice and do a fadeout. This technique works best on percussive sounds. For sustained sounds, use standard Acidization. Loop each slice individually to check that there’s only one sound or sound group (e.g., kick and snare) playing. If you hear two or more distinct sounds within the slice, slice it into smaller pieces. Go nuts with the slices! Put them on different tracks, use different processing, play with the panning, and generally have a good time.