Quite an obscure unit. Came from the German ‘BUND’ and has apparently been used to slow down tape recordings in order to be able to better understand them, especially if they were in a foreign language.
The unit itself works as a pitch shifter without changing the reproduction speed of the original material. Combined with a tape machine which changes pitch when the playback speed is altered, the original pitch can be restored, resulting in a slower playback at original pitch. This of course works also the other way around, let’s say if you would listen to a tape recording in a faster way.
It is nearly impossible to get hold of any schematic concerning this one, the only info I found was on the patents pages for variable speech reproduction.
This one explains quite well the how the concept of pitch shifting works and it is very similar to the way it has been implemented in the Varispeech unit.
I’ve been tinkering with this one for a long time and without any schematic it is quite hard to figure out whats going on. Finally I found the fault which was a bad RAM (couple of memory locations were bad). Obsolete nowadays, but I managed to get hold of a spare.
Furthermore there is this link about sound recording at the German army which also used this type of equipment and where my unit obviously comes from (pdf, in German).
I also recommend reading ValhallaDSP’s blog entry about the working principle behind digital pitchshifting: link
Here some sound examples of the sonic possibilities :
- Korg KPR77 Drummachine processed through Varispeech:
- Xoxbox Bassline through Varispeech:
- Speech processed by Lexicon Varispeech: