Locomotoring

I became fascinated with data sonification after hearing NASA’s sonification of 5000 exoplanets (link) back in 2022. Nearly 4 years later, here is my first attempt at sonification of Rosette Nebula (link), a nebula that we had caught on camera earlier in January.

What this took is Claude Code and two images of Rosette nebula, the starless one and the one with stars. I am no musician unless playing tanpura or singing bowl counts. It has been a while since I coded. To counterbalance my two handicaps, I threw in my passion for experimentation in good measure. In this image, we scan left to right and the RGB of the image is mapped to C Dorian scale.

The sound style is trying to attempt a visualization. We go from left to the right. The wiggly line is where we are creating the sound (there is some smoothing happening at a small scale) and the shape of the wiggle is determined by the local brightness.

While it is is possible to take a single final jpeg (or PixInsight’s preferred format xisf) and split it into events (stars) and drone (nebulosity). I decided to start with two images – one with stars alone and one with nebulosity alone. Fortunately, during the development of the final image in PixInsight, the stars are split off from the background nebulosity. The two require different post-processing. The stars are often minimized (e.g. exterminated) to allow the nebulosity to show through. And the nebulosity is stretched (e.g. generalized hyperbolic) to increase the inherent color contrast. The stars are relatively simple to process in the grand scheme of things. The nebulosity, in the final version, are split into RGB and “vocalized” differently.

After experimenting with the C Dorian and C Minor Pentatonic, I decided to settle for former for the RGB. Each channel is mapped to a separate octave register. Red (C3–Bb4, octaves 3-4; 131–466 Hz, Lowest — warm, mirrors Hα as structural backbone, Organ-like — all harmonics, 1/n amplitude series), Green (C4–Bb5, octaves 4-5; 262–932 Hz, Middle, bridges Red and Blue, only odd harmonics, clarinet-like) and Blue (C5–Bb6, octaves 5-6; 523–1865 Hz, Highest — cooler, airy, mirrors OIII; only even harmonics, bell like). A log scale is used to mimic human hearing. This all felt somewhat poorly informed random walk – I was the drunk trying out various scales and harmonics without any intuition.