The thirtieth instrument. Hold any letter key — that letter rings as a sustained drone tinted by a slow tremolo. Hold several at once and the page becomes a small choir; their pitches are the same vowel-and-consonant frequencies the Type Score uses.
Each voice paints a slow gilded arc across the parchment for as long as you hold its key. Release to let it fade through the hall reverb.
Try: a n d together — a major triad held under your fingers.