AdrianFreed's blog

Audio I/O programming on SGI IRIX

Integrating Sound & Graphics: Systems Issues

This note is abstracted from my 1996 Siggraph Tutorial. The media library it is based on is documented here.

Real-Time Issues

A major advantage of using dedicated hardware such as sound cards and MIDI modules is that real-time perormance and reliability issues are taken care of in the boxes.

Sewn, wearable, etextile, fabric multitouch

Piezoresistive fabric is sandwiched by sewn rows of vertical and horizontal pads using a basic sewing machine's custom embroidery pattern.

Embroidered Wireless Ball Inclinometer

This wireless variant of Hannah Perner Wilson's fabric tilt sensor uses embroidereded high electrical resistance thread . I designed the tool path to create a resistive track from the patches that can be used as a potential divider . This results in a more continuous estimate of the ball location than is suggsted by the six apparently-discrete patches.

Foucault "Knowledge is not for knowing: knowledge is for cutting."

This is why I find current historical accounts of the pioneers of electronic music so unsatisfying. So many of them use "know-that" and "know-who" accounting cutting the individual from their creative context to fit the facts into the "creative, lone genius inventor" frame. They dont fit as soon as "know-how" and "know-why" accounts are included.

"El Querreque" the Huapango musical rhythm and dance steps

"Classical huapango is characterized by a complex rhythmic structure mixing duple and triple meters
which reflect the intricate steps of the dance . When the players sing ( in duo , on a falsetto tone )
the violin stops, and the zapateo ( heels rolling on the floor ) softens.
The huapango is danced by men and women as couples; the men sing, the women do not.

You got to walk that G Chord up the neck with Mississippi John Hurt

Watch the beginning of this arrangement of "You got to walk that lonesome valley" to see how the picking pattern is modified to match the left hand

The left hand is building up and breaking down parts of the G Chord.

This continues throughout the arrangement as the  first position G Chord shape is slid up and down the neck.

G Major

Plain Barre Chord in Open Tunings illustrated by Son House

The only fretted chords in this classic Son House bottleneck blues are barres with a 7th added on the high string.

G Major
C Major
D Major


I use Drupal to share information in a variety of forms without the arbitrary size constraints of conventional hosting providers such as flickr. 

Freed Family 2009

College of Marin, California

Arduino sketch for high frequency precision sine wave tone sound synthesis

This table-based digital audio oscillator implementation illustrates a few useful techniques on 8-bit microprocessors such as the Atmel parts supported by the Arduino/Wiring IDE. A timer is used to establish the sample rate clock and PWM is used to output an 8-bit signal. Human hearing has impressive frequency precision so accumulation is done on 32-bit integers. The code is a lesson in how to used fixed point representations and careful sizing of tables as powers of 2. This reduces the computational cost of the inner loop of the oscillator to a single 8-bit multiply, table lookup and
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