Time-Stretching Loops in ACID Pro 6

Tutorial: Page (1) of 2 - 06/29/06

Time-Stretching Loops in ACID Pro 6 Making the rhythm section play double time while the overall tempo stays the same By Frank Moldstad

Drum loop
In this tutorial, the time-stretching capabilities of Sony's ACID Pro 6 will be used to dramatically alter how several ACIDized loops behave in a song. Two loops will be made to play in double time, and one loop will play in half time, all without changing the song's overall tempo.

One of the beauties of ACID loops is how they conform to the same beat when combined in a song. This is made possible by tempo data in ACIDized files that allows them to play in sync. But if you don't want a loop to have the same tempo as the rest of the song, all that's required is to misinform ACID about the number of beats in the file.

The song in question has a leisurely 88 bpm R&B tempo. After a four-bar intro, it goes into a 12-bar verse, followed by a four-bar section where the drums and bass launch into a blistering double time pace. Simultaneously, there are three guitar loops playing at their normal rate. Without the guitars, or if all the instruments were playing double-time, it would have easy to insert a single tempo change for the whole section. But that wasn't the case here, because of the mixed tempos.

Starting with the drum loop, I first placed markers at the beginning and end of the four-bar double time section. Then, with snapping set to measures, I split the drum track at the beginning and end of the section. Next, I copied and pasted four bars on a new track directly underneath. The reason for doing this on a new track is that I didn't want to change the entire drum loop to double time, just this part. Afterwards, I copied the altered clip back into the drum track (see below).

As tightly spaced beats in the green clip indicate, it's the drum track's.double time section.

A loop's beat information can be accessed by right-clicking on it and selecting Clip Properties from the menu. On the Clip Properties dialog, there's a tab called Stretch. The Stretch window has a clip editor on the right and group of parameters on the left.

For the time being, we're only concerned with the drum loop's parameter settings, which show the Number of Beats to be 16. To make it double time, this gets halved to eight beats, allowing twice as many beats to play in the same amount of time. I also entered new settings for two other parameters, Timing Tightness and Stretch Spacing. Normally, these are set for 16th notes, but I changed both to 32nd notes to compensate for the doubled tempo. There's one last very important step: a button at the bottom called Redetect Beats must be clicked. Otherwise, the changes will not take effect.

Before: Clip Properties for the drum track show 16 beats

After: Number of beats has been reset to eight. Notice how map on right has changed.

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