by Charles Gran
in three movements
for solo clarinet and electronics with improvisation

Performed by Jesse Krebs
Recorded Sunday, November 8, 2009

…Sensing Angeles was conceived as a solo piece in which the acoustic sound of the clarinet would be manipulated in real-time by a computer. Today, this isn’t so remarkable and can be achieved by a variety of means. For the project I chose to use Csound primarily as a challenge, but also for a certain kind of historical connection.

If the clarinet is an instrument with history so is Csound. A direct descendant of software created at Bell Labs in the 1950s[2], many would consider it antique in the same way the clarinet might be seen. Of course, it turns out they are both quite modern. Like most things, modernity is about use. Today, the use of a command-line interface and computer code for the creation of music is as much a point-of-view as a practicality…

Listen

I had to read the Music V manual, but I finally found the bit-depth used for the examples in Mathews’ The Technology of Computer.  12-bit, just as I suspected. According the manual, the digital-analog-converters (DAC) at Bell Telephone Laboratories (BTL) operated with 12-bit samples. (pg. 168)

I don’t recall running across a 12-bit audio-file, ever. They just don’t make them like they used.  I don’t even think Csound natively supports outputting a 12-bit file. However, it does allow us to easily simulate it with the 0dbfs opcode.

I rewrote part the CSD file from part 1 to better preserve the the original structure of the Music V example. Instead of rescaling the audio output signal of instr 1 by a factor of 16, I elminated this multiplier, and set the global dynamic range to 12-bit with 0dbfs = 2048. Original Music V amplitudes can now be used without modyifing the values or making unnecessaring changes to instrument translations. Here is the new CSD: Csound_Vs_MusicV_pt2.csd

Csound makes changing the dynamic range easy. In fact, almost all modern software allows users to choose from a list of several bit depths. Music V, not so much. When Music V was installed at a new installation, parts of the program would have to be coded, in assembly and/or Fortran, specifically for that particular system. Including the dynamic range. In theory, other computer facilities might have used a different dynamic range other than 12-bit, based on the hardware they had on site.

One interesting bit of information I discovered is something that could be considered a precursor to the modern audio buffer.

The General Electric GE645 computer at BTL used a 36-bit word length machine. In BTL’s particular setup, Music V would have to create 3 samples and collect them into a single 36-bit word before sending this word to the digital reel-to-reel. This isn’t too unlike the latency buffer found in programs such as Ableton Live, Max, Reaktor, etc., where n amount of samples are collected into a temporary buffer before sending the buffer to the DAC.