FIG. 1: The first eight notes in each chain''s key range are mapped to the white keys C3 through C4 by the Scale effect.
Slicing a drum loop or other rhythm-based audio file into individual hits, installing the slices in a multisample player, and deriving a MIDI sequence to trigger them with the same rhythm as the original is standard fare. Propellerhead ReCycle is the tool of choice for this, but you can do it in most DAWs, albeit less conveniently, by placing the target audio file and a MIDI file on adjacent tracks and slicing them simultaneously. I'll show you how to do this in Ableton Live 6, which poses some unusual challenges.
You can use any multisample player to play the slices, but Live's Impulse drum sampler offers separate outputs for each sample, has built-in time-stretching (useful when changing tempo), and can load audio clip regions into its slots. That last capability makes it unnecessary to create separate samples from your slices, though you can still do so. (See this month's “Sound Design Workshop” on p. 64 for creative Impulse tips.)
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The downside to Impulse is that it has only eight slots. To get around that, load several Impulses into separate chains of a Live Instrument Rack and precede each Impulse with a Scale MIDI effect. Set each chain's key range to one octave, and use Scale to map the eight notes C through G to the C-major scale. Then set Scale's Transpose parameter to complement the chain's key range so that Scale outputs notes C3 through C4 (see Fig. 1).
Slice by Slice
Slicing needs to be carried out in Live's Arrangement view, so create adjacent audio and MIDI tracks, and drag the audio clip you want to slice to the audio track. Set Live's tempo to match the audio clip's. (If you don't know the tempo, turn on warping for the clip and Live will make an intelligent guess.) Next, flip to the Session view, create a new MIDI clip, drag it back to the Arrangement view, and stretch it to match the length of the audio clip. Create a note at pitch C3 in the MIDI clip and stretch it to the full length of the clip (see “Step-by-Step Instructions” on p. 62).
Turn grid snapping off and place Arrangement view locators at the desired slice points. You may want to temporarily raise the audio clip gain in the clip's Sample Box as a visual aid in finding the slice points. Once the locators are in place, slice both the audio and MIDI clips at each locator. Do not use Live's Consolidate command on the audio slices. If you consolidate an audio slice, Live will normalize it, forcing you to manually adjust its level in Impulse.
Starting with the first slice, drag consecutive audio slices to consecutive Impulse slots. If you want a separate audio file for some of the slices, select Crop Sample from the contextual menu of the corresponding Impulse slot. That creates a new file without first normalizing the slice.
Select each MIDI slice and apply Live's Consolidate command. Starting with the second slice (skip the first), select the slice, then, in the Clip view, select the note it contains and nudge it twice to the right (press the Right Arrow key) and then once to the left (press the Left Arrow key). The first nudge right has no effect, and the subsequent nudging is necessary to prevent notes from disappearing when you consolidate all the MIDI slices into a single MIDI clip. After you've nudged all the notes, select all the slices (including the first) and consolidate them into a single MIDI clip.
In the consolidated MIDI clip, select each note and move it vertically to the pitch that triggers the correct Impulse slot. If you're using several Impulses, remember to compensate for their key ranges and Scale effects.
The Fun Begins
The most common reason to slice an audio clip is to change its tempo. Beyond about a 10 percent shift, you'll begin to hear gaps or overlaps between the slices. Impulse's stretch parameter, which is slice specific, expands the usable tempo range significantly. Adjusting individual slice stretching is tedious, and you can usually get away with assigning the Impulse Stretch parameter to one of the Instrument Rack Macro controls to adjust stretching for all slices simultaneously (see Web Clips 1 and 2).
Rearranging the slices is another common technique. To do that, move the trigger notes in the MIDI clip. Moving a note vertically changes the slice it plays; moving it horizontally changes the slice's timing. You can use the latter to tighten the feel or to destroy it altogether by quantizing (see Web Clips 3 and 4).
You can make subtle or radical changes by replacing some or all of the samples in the Impulse slots. Beyond that, you can route any Impulse slot to its own audio track for separate effects processing, and that even works with several Impulses embedded in an Instrument Rack (see Web Clips 5 and 6).
Set Live's tempo to match the audio clip's. Insert a MIDI clip on an adjacent track with a note at C3 extending the full length of the clip.
Insert locators in the arrangement at the desired audio slice points.
Split the audio and MIDI clips at each locator. Do not consolidate the slices.
Drag each audio slice to its own Impulse slot.
Consolidate each MIDI slice. Nudge the note in each slice (except the first) twice to the right and once to the left to separate the notes.
Consolidate the MIDI slices into a single MIDI clip and rearrange their pitches to taste.
Len Sasso is an associate editor of EM. For an earful, visit his Web site atwww.swiftkick.com.