AudioSnap™ Tech Tip - Locking Audio to a New Tempo
By Nick Dika
The original version of this Tech Tip appeared in the March 2007 U.S. Edition of Future Music magazine.

Let’s take a look at one use for SONAR 6 Producer Edition’s new AudioSnap™ feature set. While AudioSnap has been described as an alternative to Pro Tools’ Beat Detective, in this tutorial you’ll see that this suite of features goes beyond just chopping and quantizing. AudioSnap features powerful non-destructive editing, great sounding time-stretching algorithms, including iZotope Radius, and even tools that let you elasticize the tempo of your projects with ease.

So, you’ve got the stems for that new remix contest—but you want to change the tempo completely. Or, your band recorded without a click track, and now you want to add some sequenced beats. Don’t fear, just reach for the AudioSnap Palette.
Select all of your audio tracks [or hit Ctrl+A]. Now click AudioSnap enable [F12], and you’ll see transient markers appear on your tracks. Now, because we’re working with an unknown and possibly varying tempo, the next step is to set SONAR’s tempo to follow the recorded audio. Begin by choosing “Align Time Ruler” from the palette’s task list.
Next select a track with a steady rhythm (drums are a good choice). From the AudioSnap Palette, click the “Extract Timing” button to pull tempo information from this track. SONAR’s tempo is now following the track’s rhythm. If the tempo in SONAR’s transport looks double or half of what you expected, adjusting the “Expected Pulse Duration” should do the trick.
In some cases (i.e., if you only have an a cappella vocal) there might not be enough of a pulse for SONAR to find the tempo for you. AudioSnap also lets you mark beats manually. Just listen to the track you’re working with, place the cursor at the downbeats, and click “Set Measure/Beat at Now Time” [Ctrl+M] to help SONAR find the pulse of your project.
Click “Views | Tempo” [Alt+9] to see your project’s new tempo map. As the project plays back you’ll see that the transients in your AudioSnap-ed tracks now line up to the beats and measures in SONAR’s time ruler. Now, when you sequence MIDI, or drop in an ACID-ized loop, everything will follow the feel of your tracks!
Now, let’s change the tempo of your entire project. Select all of your AudioSnap-ed tracks, then click “AudioSnap Auto Stretch.” Draw a new tempo, including tempo changes if you like, into the “Tempo View.” AudioSnap time stretches everything to match the new tempo. [Remember, you can always render tracks for even higher quality by using iZotope Radius.]