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Frequency Domain Delays Sound Design Workshop

March 1, 2009

Professional-quality effects that operate in the frequency domain are rare and often quirky. But once you harness their considerable power, they give you a whole new bag of tricks with which to mangle your favorite audio tracks and synth sounds. Obelisk (Mac/Win, $125) from Artificial Audio ( is a welcome addition to the field, especially since the demise of Native Instruments' underappreciated Spektral Delay.

Obelisk uses FFT spectral analysis to slice an audio signal into either 256 or 512 frequency bands (your choice), and it lets you apply gain reduction, gating, and delay with feedback to each band separately. Moreover, the program is easy to use: you create line graphs by setting breakpoints, then animate those breakpoints with three two-dimensional LFOs. Here, I'll use Obelisk to process string, bass, and drum loops.

String Magic

When you process pulsating parts (such as staccato strings) with a delay and add some feedback, you risk having the effect take over the part. You can tone things down by using a multiband delay and applying most of the processing to the lower-frequency, less prominent bands. At heart, Obelisk is a multiband delay on steroids.

FIG. 1: This Obelisk setup applies eighth-note delay to the pink-shaded region of the frequency spectrum. Feedback applies only when that region moves into the red-shaded zone.

FIG. 1: This Obelisk setup applies eighth-note delay to the pink-shaded region of the frequency spectrum. Feedback applies only when that region moves into the red-shaded zone.

To do this, you can use Obelisk as a send effect, but I prefer to insert it in the track and use the wet/dry mix (Effmix knob) to solo the effect as I'm setting it up. Start with the gain-reduction section (called Filter), set its line style to Square, and right-click in the spectral area of the GUI to create breakpoints at 400 Hz and 20 kHz with -∞ dB reduction, and at 1,200 Hz with 0 dB reduction. You'll see a shaded pink rectangle indicating the audible range of frequencies. Set the mix to fully wet, select the breakpoints at 400 and 1,200 Hz, and move them horizontally to sweep the filter. Then set up the first two targets of LFO 1 to animate that horizontal sweeping (see Fig. 1). Notice that the shading moves to indicate the audible range, but the breakpoints and lines stay put.

Next, turn on the delay and leave its line style set to Polygon. In the Delay section, turn on 16th-note quantizing and display the grid. Then create a delay breakpoint at the second grid line from the bottom (an eighth-note delay) and roughly centered in the filter band. With the breakpoint selected (colored white), click on Quantize at the top of the GUI. The breakpoint becomes a square to indicate that when you move it, it will snap to the nearest grid line. Create another delay breakpoint roughly the same distance to the right of the filter band, but this time, raise it just slightly above the eighth-note grid line and don't quantize it. Listen to the pitch rise slightly as the filter sweeps to the right, and adjust the vertical position of the new breakpoint to taste.

Now turn on the Feedback section with a Square line style, create a 50 percent feedback breakpoint near the left edge of the filter band, and create a 0 percent feedback breakpoint anywhere to the right of the first breakpoint. That will give you multiple echoes for the lower frequencies, with single echoes for the higher, more noticeable frequencies (see Web Clip 1).

Drum 'n' Bass

Obelisk's Gate section by itself, with an LFO applied to the gate-threshold breakpoints, will add interesting timbral variation to a bass part. The factory preset Gate Swing 1 is a good starting point. It has five breakpoints distributed evenly across the spectrum, all are vertically animated, and adjacent breakpoints have opposite LFO-animation polarity. The preset has a fully wet mix, but when using it as an insert effect, adjust the Effmix knob to taste (see Web Clip 2). Moving any of the breakpoints vertically or horizontally and adjusting the LFO amount and speed are useful tweaks.

The Beat Restruction presets all use a fully wet, quantized, Square-line-style delay to reposition percussion hits that fall in different parts of the spectrum. The thing to remember when using them fully wet is that the bottom of the graph represents the original time (no delay). Useful tweaks here include adding vertical, square-wave, or random modulation to the delay breakpoints; drawing in some feedback with or without modulation; and gating or filtering parts of the spectrum (see Web Clips 3 and 4).

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

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