Clavier à lumières
The clavier à lumières ("keyboard with lights"), or tastiera per luce, as it appears in the score, was a musical instrument invented by Alexander Scriabin for use in his work Prometheus: Poem of Fire. Only one version of this instrument was constructed, for the performance of Prometheus: Poem of Fire in New York City in 1915. The instrument was supposed to be a keyboard, with notes corresponding to colors as given by Scriabin's synesthetic system, specified in the score. However, numerous synesthesia researchers have cast doubt on the claim that Scriabin was a synesthete.
The "Luce" part is notated on a treble staff with two parts, one proceeding on the circle of fifths during the piece, the other following the tonal centre of the music.