Most people of think of arpeggiation solely in melodic terms, but arpeggiation has additional uses.
General MIDI instruments include drum kits where the top notes are percussion sounds, and many virtual instruments include percussion presets. Setting up an arpeggiator in a random mode to trigger various percussive sounds can create a really cool effect. The wider the octave range, the more instruments the arpeggiator will play—which you may or may not want, if there are some annoying percussion sounds in the mix. Restricting the range, or using a non-random arpeggiator setting, can create a more "compact" set of sounds.
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