Au5-ify Anything with UZU (Spectral Phaser)

Summary

Au5 introduces UZU, a real-time spectral filter by Euan Bristo, and explains how it creates moving comb-filter effects that can transform sounds into phaser-like or laser-like textures.

• Flangers and phasers: A flanger combines a signal with a slightly delayed copy, producing harmonically spaced notches. A phaser uses an all-pass phase shift, producing inharmonically spaced notches. Both normally sweep back and forth within a limited range.
• Frequency shifting: When combined with the dry signal, a frequency shifter can move the notches continuously in one direction, but does not change their spacing.
• Additive-synth precedents: Au5 compares UZU’s effects with comb and phaser filters in additive synthesizers such as Razor and Harmor. Because these filters operate mathematically on harmonic partials, they can create spectral shapes that conventional filtering cannot.

UZU Controls and Behavior

UZU applies this kind of spectral processing to incoming audio rather than generating sound itself. Au5 demonstrates it on a saw wave and describes these controls:

• Speed and offset: Set the motion of the notches and their starting position.
• Width and depth: Adjust notch spacing and peak sharpness or resonance.
• Mix: Controls the dry/wet balance.
• Blur: Makes the effect more stepped or quantized.
• Hertz-to-octave control: Shifts the notch distribution between logarithmic and more exponential spacing.
• 5× multiplier: Speeds up modulation, enabling audio-rate, flutter-like effects.
• Keep Bass: Preserves most frequencies below about 400 Hz, which is useful for retaining a solid sub while processing higher frequencies.
• FFT buffer size: Trades time resolution for frequency resolution. Larger settings allow sharper, closer-spaced notches but introduce more time smearing and slower display updates.

Sound-Design Examples and Walkthroughs

Au5 demonstrates several uses of UZU, explaining the processing and automation in each:

1. Laser bass: Starts with a simple pitched square-wave sound, then automates UZU’s width and offset. OTT, reverb, EQ, autopan, and saturation are added afterward. Au5 notes that changing the width can also strongly alter the perceived pitch.
2. Lifter: Uses band-passed white noise, with a macro controlling UZU’s width, offset, and depth. The 5× setting increases the offset’s rotations; multiband processing and delay add further shaping and space.
3. Phaser chord pad: Uses three UZU instances in parallel, with different width settings and modulation directions. Au5 also compares the sound with and without reverb.
4. Track example: Shows UZU transforming a sustained bass into a more animated, laser-like sound by automating speed and mix.

Main speaker/source: Au5, presenting and demonstrating UZU by Euan Bristo.