Friday, 17 August 2012

Audio spectrograms with a logarithmic frequency axis

I've wanted to do this since 1990.

The Pattern Emerges by Delia Derbyshire

Detail of start of melody and chords
Audio spectrograms with a logarithmic frequency axis turn a piece of music into a picture in which the musical notes are evenly spaced up the y axis from the bass notes at the bottom to the accompaniment and melody at the top. Time runs from left to right and the colours show how much energy there is in the sound at each frequency at each instant.

This makes it simple to score a piece accurately when only its audio survives.

It's made by warping a linear spectrogram created by the sndfile-spectrogram program in sndfile-tools using ImageMagick's -fx operator.

For further details and to listen to the above piece against its spectrogram, see

Update 2016-02-22: I've modified sndfile-spectrogram to enable it to produce log-frequency-axis spectrograms directly, now included in the master version of sndfile-tools.

Thursday, 2 February 2012

Gasp! Ed written in Lua

Finally, there is a small, simple, powerful text editor written in Lua.

With no known bugs again \O/

SIEL Orchestra 2 Italian analog synthesizer

The SIEL Orchestra 2 Italian analogue five-octave synthesizer from 1983 that I found next to the dumpsters on my way home (“A keyboard,” I thought. “If the mechanism works I can probably make a software synth out of it.” I got it home and it worked perfectly, still accurately tuned after all these years) has had a hard time lately.
It suffered a fall while going from A to B one night and has lost one of its levers and three or four or its pirulini - those little brown plastic knobbly things that sit on the end of the levers. It still works, though.
Now where does one find spare classic synth knobules?!