Arpeggiator
A device or algorithm that plays the notes of a chord in sequence at a rapid, user-controlled rate, producing a characteristic "shimmering" effect.
An arpeggiator takes a chord — multiple notes held together — and plays them up, down, or in random order at a fixed tempo. It lets a musician play a single key and hear a musically coherent figure unfold. Tracker composers in the 1990s used arpeggiation heavily to create harmonic movement without burning CPU cycles; a few notes arpeggiated at the right speed could suggest a melody that actually plays just one voice. It remains a chiptune staple because it is simple, cheap, and musically convincing.