When I decided to get an Eigenharp, it was with the intention of mainly using it as a controller for my existing hardware instruments. Controlling hardware synths with polyphonic multidimensional controllers seemed to be less than ideal because of the limitations of midi, so I was a bit worried this might not work out as well as I had hoped.
Luckily, my worries were mostly unfounded. In particular, the Analog Four turned out to be a decent partner for the Tau. The A4 is a small, 4 voice analog desktop synth tightly integrated with a powerful step sequencer. The synth engine itself is decent, but on its own not all that exciting. It is in combination with the sequencer that it really shines. It does, however, have a couple of unusual features that might be of interest for owners of one of the multidimensional controllers.
One of them is that it has four configurable CV outputs. I set them up to respond to pitch, modwheel, aftertouch and breath on a specific midi channel so that I could play my modular with the Tau. On paper the A4 supports 14bit for the types of messages I used, but a firmware bug means only 7bit modwheel CCs can be used at the moment.
A limitation of midi means that a single channel of midi data can’t be modulated independently. A single note of a chord can’t be pitch bent alone, for instance. All notes of the chord would be bent simultanously. To overcome this, multiple midi channels needs to be used, one for each voice. This is often referred to as “Voice per Channel”, or “VpC”. The A4 is at heart four mono voices, so VpC setup is simply a matter of loading the same sound four times. Also, all four voices combined are stored together as a “kit”, which can be changed by a program change msg or single keypress. So one can have a collection of kits that one basically can treat as VpC presets.
When loading a preset to a kit, the kit keeps a separate “copy” of the sound for each of the four voices. This means that tweaking a preset and saving it on one channel doesn’t update the other three. Reloading a preset to the remaining channels is just a couple of quick button presses, but I keep forgetting to do so. So when editing a sound I need to turn off VpC, play the patch monophonically until I’m happy with it and then save and reload. A minor inconvenience, but one that most synths synths wouldn’t have.
The A4 is designed to jump back and forth between lots of different sounds on a single, monophonic channel without glitches. It also has a multimap feature that maps various presets to specific notes. I use this to play a collection of drum sounds from the percussion keys, but since the multimap feature also allows for specific notes to switch patterns, specific keys can be used for song arrangements and selecting kits/presets as well.
Lastly, Elektron recently released “Overbridge”. What that does is integrate the A4 with a computer via USB. It allows the A4 to act as a sound card if one wants it to, and it also adds a VSTi that remote controls all parameters of the synth. As an experiment I loaded the VSTi in EigenD and controlled the CV outputs directly, avoiding midi altogether. It worked as expected, meaning I could bypass the 7bit midi CC restriction and control my modular with much higher resolution.