About the music

01. Toccata and Fugue in D minor

Two 6581 chips.

The toccata is perhaps the most well-known work in the entire organ repertoire. Like many toccatas, it is probably a transcribed improvisation. It has been postulated that this was a test tune that Bach would play when trying out new organs. That would explain its crude character and the various hops between heavy chords and rapid melodic parts.

The fugue is written for four voices, and the subject resembles a passage in the toccata.

02. Ich ruf' zu dir, Herr Jesu Christ

One 6581 chip.

This is a chorale prelude from Orgelbüchlein. The chorale itself is a very simple melody, so the praxis is to embellish it with trills and other ornaments. Thus, my interpretation will be different from other recordings you may have heard.

This piece of music was featured in Tarkovsky's film Solaris.

03. Contrapunctus 1 from Die Kunst der Fuge

Two 8580 chips.

Die Kunst der Fuge is a terribly clever suite of fourteen fugues and four canons, of increasing complexity, all based on the same theme. This is the first piece in the suite, so it is a comparatively simple four-part fugue.

04. Allein Gott in der Höh' sei Ehr'

Two 6581 chips.

Bach has based at least ten different works on this melody (BWV numbers 662, 663, 664, 675, 676, 677, 711, 715, 716, 717), presumably quite varying in style and harmonic content. This version is a chorale prelude.

05. Passacaglia and Fugue in C minor

Two 8580 chips.

The grand finale!

A passacaglia is based on a short melody which is repeated throughout the piece, mostly in the bass, sometimes with variations. In classical music, this type of prolonged repetition of a single theme is called an ostinato. In contemporary music, it's not called anything at all, because it is implied.

The fugue is quite advanced. The subject is the first half of the ostinato from the passacaglia. Everytime the subject sounds, two counter-subjects can also be heard (except in the very beginning of the fugue), while the fourth voice joins the others in free counterpoint. These four roles — playing the subject, playing the first counter-subject, playing the second counter-subject and playing free counterpoint — can be distributed among the four voices in 24 different permutations. This happens eleven times throughout the fugue, and Bach picks a different permutation every time according to a mathematical formula. Can you find it?

About the technology

It struck me that, at least in theory, organ pipes should generate quite primitive sound waves. If so, how come a church organ doesn't sound like a chip tune, which is also built up from simple waveforms? Well, actually it will, if you remove the church. And if you connect a Commodore 64 home computer to a loudspeaker in a large hall, it will sound like an organ.

So the music on this album is not performed on a pipe organ. Instead, what you hear is the sound of one or two SID chips (controlled by a Commodore 64), enhanced by a convolution reverb to simulate church acoustics.

Quantization

There is already an abundance of SID tunes based on sheet music, in particular by J. S. Bach. The problem is that all those SID tunes are terrible. Apparently, people have merely typed in the notes from the sheet music. This leads to quantized timing (where e.g. every quarter note lasts exactly 500 milliseconds, always), and while quantized timing may be perfectly fine for modern genres, it simply won't do for classical music.

The goal is not to play the right notes in the right order; that's the starting point. Then you have to adjust the timing of every single note, listening and re-listening, making sure that it doesn't sound mechanical. You have to add movement, energy, and emphasis (which, on an organ, has to be implemented by varying the duration of the notes, and the pauses between them, because there's no dynamic response). You need fermatas and ornaments. You have to realize that some jumps cannot be performed unless the organist lifts his hand, and so on, and so forth.

This album is an attempt to demonstrate that classical music can indeed be performed by a computer. But the amount of work that goes into programming the computer will never be less than the work that a traditional performer would put into studying the same piece of music.

Registration

In general, I've opted for fixed-width pulse waves for the manual voices, and a pulse hard-synced with a triangle wave one octave below for the pedal voice. Some waveforms are run through a combined low-pass and band-pass filter with moderate resonance. In Allein Gott and Ich ruf zu dir, I use a narrow pulse wave for the cantus firmi and unfiltered triangle waves for the accompaniment.