Tokøta from Mastering.com walks through Alchemy's AR tab, the arpeggiator built into Logic Pro's flagship synth, and how it applies to every layered source at once rather than one sound at a time.
Six modes cover the basics: up, down, up-and-down, as played (following the order you actually hit the notes), random, and chord, which just restates the full chord on each step.
From there it's the same core controls as Logic's step sequencer: rate, swing, octave range, note length, and velocity, all shaping how tight or loose the arpeggio feels.
Pattern switching lets you flip between 16 saved variations on the fly, a fast way to build movement into a part without reprogramming anything.