Granular fun with Alchemy

A granular instrument is essentially a sampler on steroids. Here’s how to use Logic’s four-osc virtual beast to mangle audio

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Choose File >> Initialize Preset. The instrument’s four oscillators, called Sources, are capable of multiple synthesis and sampling types. Click Saw A’s top header and choose Import Audio to open the Import screen. After setting the bottom Analysis Mode to Granular, hunt down a vocal sample and punch Import.

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Bash MIDI notes, and Alchemy plays back the audio, sampler-style. Set Speed to 0%, then sweep Position to move the playhead through the audio file. Now to the right Granular controls: set Density to 1, and a single grain is output once the previous one has finished. Sweep Size from the minimum 2ms to the max 230ms to lengthen and shorten the grain.

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So far, we’ve just been repeating one ‘chunk’ of audio. Density defines how many grains will be played back at once (between one and 10) at the playhead position. Set Density to 10 grains, then play a chord while sweeping or modulating Size. This ‘fluffiness’ can be perfect for synthesising those soft, ethereal, pad-like timbres.

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For stereo interest, flip the Source’s Mono/ Stereo button to Stereo mode, then raise the Granular >> Random Pan (RPan) knob. The pan position of each grain is now randomly offset for a lush stereo effect. And, as you’d expect, ‘granularised’ signals like this sound gorgeous when doused in reverb and/or delay.

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Shorter Size values can result in harsh, atonal effects. To combat this, granular synths automatically crossfade each grain, reducing harshness and shaping grain-to-grain timbre on a microscopic level. The fade ‘curve’ of this crossfade can be changed, however: choose from eight Grain Shapes via the menu.

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The RTime knob randomises grain playback position. A short Size value and 0% RTime creates obvious buzzing, because the grains are simply repeated. Raise RTime and the signal turns ‘fluffy’ again. From here, modulate granular parameters and playback Position for timbral interest.