Prometheus: The Poem of Fire, Op. 60 (1910), is a tone poem by the Russian composer Alexander Scriabin for piano, orchestra, optional choir, and clavier à lumières or "Chromola" (a color organ invented by Preston Millar, in fact rarely featured in performances of the piece, including those during Scriabin's lifetime). Prometheus is only loosely based on the myth of Prometheus. It premiered in Moscow on 2 March 1911. A typical performance lasts about 20 minutes. Structure The music is complex and triadic only in an idiosyncratic sense, based almost entirely around various inversions and transpositions of Scriabin's matrix sonority: A D G C F B. Sabaneyev referred to this chord, which opens the work in an eerily static fashion, as the "chord of Prometheus". It has subsequently become known as the "mystic chord". But after unrelieved dissonance throughout, the symphonic poem ends with a resplendent F-sharp major triad, the only conventionally consonant sonority in the entire composition. Color organ The part for color organ is notated on a staff of its own, in treble clef at the top of the score, and consists of two parts: one changes with the harmony, and always goes to the root note of the prevailing harmony, and thus produces the color Scriabin associated with each key; the other consists of much longer notes sustained through many bars, and does not appear to be related to the harmony (or therefore to the first part), but for the most part slowly rises up the scale a whole-tone at a time, the changes being several pages of score apart, or a minute or two apart. It is not clear what relationship this part has to the first part, or to the music as a whole. The score does not explain how two different colors are to be presented at the same time during a performance. This color organ part also contains three parts briefly at one point in the score (Bars 305-308). Sources differ on what Scriabin's intentions were for the realization of the color organ part: many state that the colors were meant to be shown on a screen in front of the audience; but others say that the colors were intended to flood the entire concert hall and that showing them on a screen was merely the compromise adopted after flooding the concert hall was found impossible or impracticable. The score itself contains no indications