Strum plate

A strum plate has no strings. It is a flat strip divided into touch zones, each playing one note, running from low at one end to high at the other. Sweep a finger along it for a run of notes, or tap one spot for a single note. A quick sweep sounds like a harp glissando, and a slow one plays the chord as an arpeggio.

The idea comes from the autoharp, where a chord bar mutes every string outside the chord so a strum sounds only that chord. On the Omnichord, the plate plays the notes of the chord you hold across about four octaves, and every zone changes note when you change chord. Hold C and a sweep plays only Cs, Es and Gs, rising from low to high. Switch to G7 and the same sweep plays Gs, Bs, Ds and Fs. No zone can play a note outside the chord.

Gelato Chord, our iPhone app, has a melody plate that works differently. Its twelve strings are the notes of your key’s scale, and they never change. The strings that belong to the chord you hold light up: in C major, holding the F chord lights the F, A and C strings. Sweep across for a run (a faster sweep plays louder) or tap single strings for a melody, and the unlit scale notes between them are there when you want them.

You find strum plates on Omnichords old and new and on phone apps that copy the layout. 7 Omnichord apps for iPhone puts the phone versions side by side, and what is an Omnichord covers the original.