AndreasKrebsBlog

This is a piece of music with two sequencers being slightly out of sync (and with independent master clocks). As you can imagine, this was to some extent inspired by ideas Steve Reich already had in the sixties.

Instruments used: Doepfer A-100.

Right from the beginning, we hear two voices spread in stereo: both are controlled by two independent A-155/154/156/150 Sequencers (Sequencer, Controller, Quantizer and Switch for 16-Step mode). Clock frequencies have been manually adjusted and will drift during the piece. Both voices are quite similar, each one is based on three A-110 VCOs (all VCOs: individually modulated pulse waves, same ocatve), mixed (A-138b) and put into two different filters: An A-105 SSM Lowpass for the voice panned more left and an A-102 Diode Lowpass (with its beautiful “crystal” overtones) for the voice on the right side. Both go through A-131 VCAs, and finally into an A-138m Matrix Mixer. VCAs and filters are controlled by A-140 ADSRs, triggered by the (active) sequencer steps and by another A-140s, triggered when the sequencer switches from steps 9-16 back to steps 1-9 (using the resp. Sequencer Controller trigger and inverting it).

After a while, I’m adding some slight BBD delays to both voices - done with an A-188-1D and an A-108 for the left side and an A-188-2 and an A-108 for the right side (the A-108s are used to filter the BBD-internal clock noise which is quite audible with low clock frequencies as used here). Delays are mixed to the opposite pan position (left voce’s delay will appear on the right side) via A-138m.

If you already know some of my music, it will be no surprise that “music” will start after no less than two minutes: I’m adding additional sequencer steps. As soon as I do this, there’s some additional percussion: it is triggered only when the Quantizers (used for the sequencers) begin to detect different notes. I’m using both rising and falling edge of the A-156 Gate signal (via A-165 Trigger Modifier). Again, we have a percussion voice connected to the sequence panned left and one for the sequence panned right. Left: an A-117 Digital Noise put through an A-106-5 SEM Filter (LP mode), an A-188-1X (for some flanging) and an A-132-3 VCA. Filter and VCA are controlled by an A-140 ADSR. Right: an A-118 Noise (colored) put through an A-124 Wasp Filter (HP mode), an A-189-1 VC Bit Modifier and an A-132-2 VCA (also with A-140).

Finally, we hear some pad-alike sounds (again separate voices for left/right). Left: An A-111-1 VCO through an A-137-1 Wave Multiplier I (modulated by an A-143 Quadrature LFO), an A-101-3 Vactrol Phaser (12 Stages used with two different LFOs), an A-106-6 XP Filter (2 pole LP mode) and an A-132-3 VCA. Right: An A-111-1 VCO through an A-137-2 Wave Multiplier II (modulated by another A-143 Quadrature LFO), an A-127 Triple Resonance Filter, an A-121 Multimode Filter (LP mode) and an A-132-3 VCA. Here, I’m using two A-142 VC Decays put through an A-170 Slew Limiter (since I wanted to have long attack phases even with very short gate signals) as VCF and VCA envelopes. Triggers are created by some logic AND operations of left and right side sequencers (A-166 Logic, A-152 and A-160/161 Clock Sequencers as well as manual gate length adjustment via A-162 Trigger Delay are used for this). Pitch of the pad voices is created by two random generators in an A-149-1 RCV module sent through the two Quantizers mentioned above (internal jumpers are set for similar operation of both quantizer channels - thus I’m using “minor chords” quantisation for all four pitch control voltages).

The rest are variations on sequencer lines (with increasing complexity), expanding tonal ranges, some fooling around with BBD delay times, etc.

Here we go:

 http://www.andreaskrebs.de/assets/media/improvisation-20110418a.mp3

Track length: 16:21.

Have fun,

Andreas

The A-102 is a 24 dB lowpass which uses diodes (and not transistors), which leads to quite unusual resonance behaviour (resonance is dependant on filter frequency). The filter can easily be overdriven, which adds some interesting harmonics. In this sound example, I use three A-110 VCOs (sawtooth, one VCO tuned down 1 octave), mixed and put through the A-102 and then into an A-132-3 VCA. Both VCA and filter are controlled by an A-140 ADSR, the sequence is made with an A-155/A-154 Sequencer.

Technical details on the A-102 can be found on Doepfer’s Homepage:

http://www.doepfer.de/a102.htm

• We start with comparably low input level, no resonance and cutoff frequency at minimum. Then I manually increase cutoff frequecy up to maximum and back to zero.
• Starting around 0:35 same procedure, but with medium resonance (value ca. 3)
• From 1:10 on: full resonance.
• Then back to zero resonance, but from 1:50 on maximum input level.
• Starting at 2:25 we hear medium resonance again (full input level).
• Finally, around 3:05 we have max resonance and max input level.

Here we go:

http://www.andreaskrebs.de/assets/media/A-102.mp3

Have Fun, 

Andreas

The A-111-5 is a “Dark Energy” in Eurorack format (without Midi and wooden side panels). This is a nice and versatile module: quick sound changes are possible without patch cords, overall sound is very good and the filter will follow 1 V / octave extremely well, thus being something like a “second VCO” when self oscillating. Technical details can be found on Doepfer’s homepage:

http://www.doepfer.de/A1115.htm

I’m using an A-155 Sequencer together with an A-156 Quanzizer to tonally control both VCO as well as VCF of the A-111-5. So we have some kind of “twovoice synthesizer” in that little box. I start with the pure filter sound (self-oscillating), then I add the VCO (pulse wave) and later some LFO modulations of VCO / VCF). Finally, filter resonance is reduced until we only hear the VCO. No additional processing was necessary. Here we go:

http://www.andreaskrebs.de/assets/media/A-111-5-twovoice.mp3

Have fun, 

Andreas