Impulsive Decisions

Using Ableton Live's Impulse with sliced loops.
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Ableton Live's Impulse drum sampler makes an excellent player for sliced audio files because of its ability to apply separate processing and output routing to each of its slots. In this month's “Making Tracks” column (see p. 60), I show how to slice audio files directly in Live and combine several Impulses in a Live Instrument Rack to reach beyond Impulse's 8-slot limit. Here I'll give some tips for making the most of that rack.

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FIG. 1: The Live Instrument Rack (right) -contains four Impulses in parallel. The -Random MIDI effects (left and middle) ensure that the Impulses are selected equally.

I have based my examples on a rack that contains four Impulses triggered by the first eight notes in the C chromatic scales (C through G) starting on C3, C4, C5, and C6, respectively (MIDI Note Numbers 60-67, 72-79, 84-91, and 96-103). Web Clip 1 contains such a rack. The most straightforward way to use that rack is to arrange the trigger notes for the resulting 32 slots manually, which is what you'd do with slices that have been sequentially carved out of a single audio file.

A Better Alternative

You can also fill each Impulse with alternative slices from similar loops. Many MIDI loop collections come with several variations on the same basic loop. The timing of the slices in these variations is usually close enough for you to use the same trigger file for any variation. In that case, you can redirect the trigger notes on the fly to mix the variations, and Live's Random MIDI effect is perfect for that.

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The Random effect shifts incoming notes by some interval, and four parameters (Chance, Scale, Choice, and Sign) determine that interval. Chance sets the probability of a shift occurring. Scale sets the smallest possible shift interval, and Choice specifies possible multiples of that shift interval. Sign determines the direction of the shift (Add for up, Sub for down, and Bi for either [see Fig. 1].

To choose between the four Impulses, use two Random effects in series, set both Sign buttons to Add, both Choices to 1, and their Scale knobs to 24 and 12. The first Random effect shifts the focus between the first and second pair of Impulses in the rack. The second Random effect shifts the focus within the chosen pair. Together, the two Chance knobs set the probability of each Impulse receiving the incoming note, which should always be between C3 and G3. For example, with both Chances set to zero percent, the top Impulse will always be used. With both Chances set to 50 percent, each Impulse is equally likely to receive the note.


You can use Impulse's individual slot parameters to add variation to your slices; Transpose and Stretch work especially well. Use them with the Mode switch to control the amount of pitch-, timbre-, and time-shifting. Using a notch filter with a high Random setting is another good option.

You can apply effects plug-ins in various ways. You can insert plug-ins after the Impulses in the rack to apply them to all slots, but I prefer to create additional Live tracks, route a whole Impulse or individual Impulse slots to those tracks, and apply insert or send effects on the added tracks.

Beat Repeat is one of my favorite Live effects to use for processing percussion. If the slices are evenly spaced in time, setting the Interval knob to the slice length will cause each slice to be processed with the probability set by the Chance knob. The effect is determined by the remaining controls. Try midsize Variation settings in Auto mode and experiment with the filter and Pitch Decay settings. If Beat Repeat is a send effect, use its Gate mode; otherwise, use Mix or Ins mode, respectively, for a more- or a less-dense effect.

Grain Delay and Auto Filter are good to use when applied to individual slots. Their effects can be radical, but with each Impulse getting only 25 percent of the action, the effects are used sparingly. Don't overlook each effect's x-y Controller; that's a great way to adjust the effects in real time. With Auto Filter, use the Phase, Offset, and Spin controls to affect the filtering relationship between the stereo channels. Also note that the Quantize Beat setting determines how often the modulation updates and is independent of the modulation rate, even when that is set in note increments (see Web Clip 2).

Len Sasso is an associate editor of EM. For an earful, visit his Web site