The Melting Sun is an ambient composition in the Bohlen-Pierce scale, whose tonality, timber, volume, and timing are determined algorithmically from a video of the sunset.
The sounds heard can be separated into two groups: the drones, and the melodies. Both groups feature three different Csound instruments that each correspond to various types of Red, Green, or Blue values extracted from the video. These data, combined with the data gathered from the position of the sun, control various parameters of the composition. Some of the data mapping choices are arbitrary, and some are obvious (i.e. the overall brightness controls the cutoff frequency of the global filter for the drones).
The composition is in the Moll II mode of the Bohlen-Pierce scale. The note numbers used for the drones and the melodies are predetermined, but the base frequency of the scale is not. In fact, the base frequency, or the tonality of the composition, shifts continuously throughout the piece with sun’s position, but the process is too slow to be perceptible—just like the movement of the sun itself. The three melodic instruments actually play the same long loop of notes, but at different timings and also in different tritaves. The timing itself changes continuously, and as the sun comes lower in the sky and causes an illusion that it is gaining speed, the notes are played more frequently. The composition currently uses previously recorded video material, but in the future it will allow the use of a visual live feed of the sunset.