Spectrograms of Cristian Vogel’s album Eselsbrücke (2013)

Cristian Vogel asked whether I’d created spectrograms of his album Eselsbrücke (2013).
I hadn’t, so I did. Here’s the results.

The album was conceived around a structural arc, and each track is also highly structured, based on formal processes such as number sequences derived from the ‘sieve’ method developed by Iannis Xenakis. Xenakis’s own explanation of sieves in Formalized Music is notoriously impenetrable, but Cristian Vogel provides a clearer description of these methods in the article Donkey Bridges: On Creative and Technical Process Behind “Eselsbrücke”

The spectrograms I made all use a logarithmic frequency scale, which provides a closer parallel to the way we hear frequencies than a linear scale (octaves appear equally spaced, rather than increasingly spaced out at higher frequencies). Using Sonic Visualiser, the settings were:

Window type: Blackman-Harris
Window size: 8192 samples
Window overlap: 93.75%
Oversampling: 4×
Amplitude scale: dBV^2
Frequency scale: Logarithmic

After creating a spectrogram for each track, I put them together using IrfanView to show the album structure as a whole. In the image below, you can see the roughly symmetrical structure of the album. You can also see patterns within tracks, like the arcing lines that represent formal structures based on number sequences transformed to pitch. These curving patterns occur in repeated sounds where tempo (or rate of repetition) is proportional to pitch and the phases of the tempos are aligned at some point. You can also see these patterns in this post where I visualized tracks based on the harmonic series. Where these patterns make an inverted U shape in the spectrogram, it indicates that tempo is proportional to pitch, with the lower parts having lower rates of change. When the pattern is a U shape, tempo is inversely proportional to pitch, and the higher parts have lower rates.

This kind of visualization is something I’ve done previously for two of my own albums: With Symmetry-Breaking it revealed the symmetry (and lack of it) in the tracks and the album structure, e.g. that the last track is the first track reversed. With Complexification, a collaboration with Sun Hammer where we started by making a simple track each and then using the other’s track as the basis for the next, it showed how the music evolved with each phase of the process. 

[Edit:] After I posted this, an image of the score for James Tenney’s Spectral Canon for Conlon Nancarrow popped up on my Twitter feed. At the end, it shows the same kind of curved structure as described above, with lower notes being repeated less frequently than the higher notes:

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1 Response to Spectrograms of Cristian Vogel’s album Eselsbrücke (2013)

  1. Pingback: EVOL – The Chord Catalogue for Eight-O-Eight | Aesthetic Complexity

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