In memoriam

Here can be found the most wonderful music created on the computers DATASAAB D2, D21 and D22. The material is recorded from an EP released to the memory of the D21 and D22 at Kraftdata and recorded in 1967 (D21) and 1970 (D22).

Software for playing of these files under DOS, Windows, OS/2, Mac, Amiga, BeOS and a number of unix flavors can be found here.

A note on the quality:
Pieces marked by * are of significantly better quality than the rest. The reason for this is that these have been re-sampled using a lot better equipment. The other's files were regretably lost due to unfortunate circumstances after the re-sampling, but I hope to get the opportunity to re-sample those as well within a near future.

COMPUTER MUSIC created on the DATASAAB D21 and D22 computers

Since the functions in a computer is controlled by an exact quarts-crystal clock, it's easy to construct program frequences to be executed with a determined time base. The D20 computers works according to the binary system with ones and zeroes represented by electrical pulses. By connecting an amplifier and loudspeaker to a specific numberposition in the machine these impulses can be made audiable. From school physics we remeber the connection between frequency and time as f = 1/t. To get the tone middle a with the frequency 440 Hz you feed the amplifier with impulses with an interval of approximately 0,00227 seconds. In the same manner the other tones's intervals are calculated. It's easy as long as you play with only one part and it's not possible to play more than one tone at the same time. One way to get around the problem is to repeatedly play the diffrent tones in a chord individually. The echo of the tape will make the ear hear it as the tones were sounding at the same time.

A better way to accomplish polyphonic sound is to use a so called digital to analogue converter or just dac. It's an output-device which translates the computers representation of numbers to an electrical current corresponding to the number sent. Normally the dac were used to control for example a plotter. With the tonalstring with the dac you have full control over the tonal curve and can add many tones amplitudes before the output.

[dancing]

D21 in memoriam

The D2 heritage (0:30/mono/236K)
The D2 was the first transistor based computer at SAAB, developed in the late 50's. It had limited memory why the time base for the different tones was fetched from the paper tape reader with the side effect of it beating the time.

Christmas Songs (1:07/mono/524K)
An attempt top play many tones at the same time by quickly switch between the different tones in a chord.

Mozart: ''Ein musikalisches Würfelspiel'' [A Musical Game of Dice] (1:39/mono/628K)
A system for the composing of waltzes developed by Wolfgang Amadeus Mozart as diversion. He compiled a set of notes with numbered bars. There were also a table and two dice. After every roll you checked the table for the bar to be played. The sound of the waltz was completely random. The rolls of dice are randomized by the computer.

Mozart: Würfelspiel, the second try (2:13/mono/912K)
Now with a tonal string over a digital to analogue converter.

D22 in memoriam

Stereo Test (0:19/stereo/266K)
One can imagine an organ with the pipes for the difrerent tones placed from left to right.

Mozart: Würfelspiel, the third try (4:58/stereo/4106K)
Here with a digital to analogue converted tonal string where the curves for the different organ voices are calculated by adding the sine waves which make upp the key notes and overtones.

Register possibilities, voices and the partial tones relative amplitude

	Key note	Overtone	1	2	3	4	5
Flute	8'	100	0	0	0	0	0
Hole flute	8'	90	30	0	0	0	0
Chamois horn	8'	30	40	20	10	10	0
Trumpet	8'	20	25	30	15	0	0
Principal part	8'	20	20	15	10	5	0
Salicial part	8'	40	20	20	20	10	0
Strings	8'	0	20	20	20	20	20
Oboe	8'	15	30	35	25	10	5

The waltzes are played quadrophonic in stereo and the timbre is changed after every recapitulation.

J.S. Bach: ''Bist du bei mir'' from Notenbüchein Anna Magdalena Bach (0:49/stereo/672K)
Funeral music to the end of the D20 era.

Most of the text on this page is taken from the record's cover and then translated into English.

By calculation

* By calculation (3:10/stereo/2970K)
The composition performed by a computer was made for the opening of SPADAB's central in Malmö 18 April 1967.

Göran Sundqvist, producer, arranger and programmer of this music.
Göran began working with computers at the SAAB electronics department in the end of the 50's, where he took part in the development of the D2 and later the D21.
In 1962 he went to Skandinaviska Elverk in connection with the first D21 installation.
1979 Skandinaviska Elverk's computer department was transformed into Kraftdata where Göran worked until 1993.
A big thanks to Göran Sundqvist for his work with the programming and recording and for his permission of using the music here.
Many thanks also to Göran Sedvall at the department of computer science at Linköping University for the recording of this record on which these files are based. The original can be seen in a showcase at the Datasaab exhibition in the hallway which connects the B and E buildings at Linköping Institute of Technology. Thanks also to Daniel Högkvist and Linköping's student radio for the re-sampling.

Magnus Karlsson

Last modified: Mon May 24 21:45:32 MET DST 1999