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RE: tape looping/tape delay KLANGUMWANDLER

Title: RE: tape looping/tape delay KLANGUMWANDLER

 >> Thanks Stephen for the post about the "klangumwanler." [snip] The only stuff I seem to turn up on google is lots of Wendy Carlos stuff and a few very casual mentionings of the work klangumwandler. Do you think this would be tricky to build? The one I saw in "How Things Work" looked like a detachable or retrofit unit. It seems that one would have to come up with some kind of a circular "railroad track" kind of brush that the contacts for head could ride in [snip]

a small keyboard controller for the motor speed of the unit.....<<

I have a vague recollection of that ampeg device too..... but for the former, hopefully the following will satisfy:

I have searched instead on the old interweb for mention of a device I knew as "eltro". I first saw mention of this thing, made IIRC by a german or austrian company (AEG? AKG? telefunken? EMT, as it turns out, the same people who made the reverb plates), in the glossary section of the booklet that came with "the nonesuch guide to electronic music".

this double LP set was "realised" by beaver & krause on an early-ish moog 3-series & is probably quite rare.
the "eltro" was explained as a tape-device for independent alteration of pitch & tempo. I had a much higher IQ back in those days (when I was 9 or 10) & figured that such a device would need a rotating head system. paul & bernie didn't have one, but I bet they wished they had.

I have, like steve, seen pictures of this device, though I can't recall where.... the bbc radiophonic workshop had one, which attached somehow to the side of one of their regular 1/4" decks (a philips- seems they made broadcast decks too, back in the day).

rotating heads used to operate with brushes as steve describes, but since the early days of vtr (late 50s), rotary transformers have been used instead. basically, the head assembly is constructed with a cylindrical transformer coil around it, & the whole assembly spins within a static secondary coil.


this from the AES.org timeline of recording-related inventions:


    * The Dolby Type A noise reduction system is introduced.

    * Robert Moog shows elements of his early music "synthesizers."

    * Eltro (Germany) makes a pitch/tempo shifter, using a rotating head assembly to sample a moving magnetic tape.

    * Herb Alpert and the Tijuana Brass tour with a Harry McCune Custom Sound System.

while this pdf for a recent dolby pitch-shifter mentions the "emi eltro" in passing, while describing an altogether more mundane requirement for independent pitch/time shifting.


a more detailed discussion from this 78s forum:

(but save yourself the effort, it's pasted below)

& this thread, but note it's the same machine at gotham recordings.... interesting anecdotes about the beatles & sam cooke in the autotune debate too.


Date: Wed, 5 Nov 2003 23:28:39 -0500
From: "MICHAEL BIEL" <mbiel@kih.net>
Subject: [78-l] Analog tape pitch shifter (was: Digital Toscanini)

I have one of the machines, it does work, but the sound IS atrocious.
There were several different versions. The one I have is called the
Whirling Dervish. I understand that the original AEG Magnetophon K-1 from
1935 also was such a device. The first one I saw was the ELTRO that Jack D
mentioned. It demonstrated by Steve Temmer of Gotham Audio in at a meeting
I attended in 1967, and years later the company was able to refer me to
Steve's retired partner who coincidentally knew of me thru my Ph.D.
dissertation. (Trying to remember the name.) He told me that the Univ of
Louisville had one, and I went to see it. The following year when they
decided to get a digital harmonizer, they called me up and offered the old
one to me. I am not sure what the relationship is between the ELTRO and
the Dervish, but apparently Gotham sold the latter when the ELTRO became

The Whirling Dervish is slightly different from the ELTRO that Jack
described. It doesn't need to have a separate tape recorder. It uses a
continuous loop of tape in a bin-loop. There is a huge capstan, and the
speed can be varied from probably 20 to 60 IPS. There is a stationary
erase and record head, and a head-wheel with the four playback heads set 90
degrees apart. These are mounted in a spindle about a half inch in
diameter. It is run by a separate motor and can be spun in either
direction. Only one of the four heads contacts the tape at any time. If
the heads are stationary, the playback is at normal pitch. If the heads
turn against the direction of the tape movement, the relative speed of the
tape to the heads is increased, so the pitch is raised. The tape moves so
fast and the heads can spin so fast that there are little tiny slivers of
sound that are skipped over as one playback head leaves the tape and
another picks up the playback. If the heads are spinning in the direction
of the tape movement, the relative speed is decreased and the pitch is
lowered. Tiny slivers of sound are repeated. By adjusting the capstan
speed, the headwheel speed, and a switching device they called the
smoothing control, you can eliminate most of the jitter effects of the
missing or added sounds. It works best with speech, which is what the Univ
of Lvl was using it for. They were experimenting with finding the
acceptable rates for compressing speech for readings for the blind.

This is a pitch shifter, and will work with live sound or with a recording.
It will raise or lower the pitch of a live sound or a recording played at
proper speed. This would enable you to fix the pitch or the key of the
music without altering the tempo. On the other hand, if you change the
speed of the playback of the recording you are feeding into the machine,
you can use the pitch shifter to restore the pitch to normal. Thus you can
play a recording either faster or slower in tempo and then restore the
pitch to the original key. As I said, they were used for compressed speech
for readings for the blind for many years before the digital methods were

Mike Biel mbiel@Kih.net

>>>> I understand there was such a method. It involved a tape
>>>> player with heads mounted on a wheel that spun.
>>>> The tape would move at the normal playback speed,
>>>> and the motion of the heads relative to the tape would
>>>> either raise or lower the pitch.
>> >
>>>There must have been more to it than that! On an analog tape,
>>> the pitch depends on how fast the tape is passing the playback
>>> head, it doesn't matter whether the tape is moving across a
>>> stationary head, a head is moving against a stationary tape
>>> or a moving head is passing a moving tape.
>> I agree that the pitch depends on the relative speed between
>> the tape head and the tape. Let's say the tape moves at 7.5 IPS,
>> and the spinning wheel moves the tape heads at 1.5 IPS in the
>> opposite direction of the tape motion. The speed of the tape
>> relative to the heads is 8.0 IPS, so the pitch would be higher
>> than if the heads were stationary. But the tempo wouldn't be
>> affected, since the tape still passes by at 7.5 IPS.
> From: <jackson32@mindspring.com (Jack)>
> In 1967 at Gotham Recording in NYC we had a "Rube Goldberg"
> arrangement called "ELTRO" stashed away in a small studio.
> It could do pre-digital tricks and involved the use of two tape
> recorders. My recollection of it is a bit hazy because we didn't
> use it often & I didn't get to use it at all although I did see it in
> operation one or more times.
> I think the original intent was to alter time without changing pitch.
> This would have been most useful in time-editing voiceovers and
> commercials which were a major part of Gotham's business.
> If I recall correctly it involved playing the tape on a variable speed
> equipped Ampex while threading it through the head assembly of
> an externally mounted and modified tape machine (a Tandberg
> with a rotating playback head, a la VTR, I believe) & back to the
> Ampex's take up reel. If the tape were stationary, the sound at the
> rotating playback head could be sustained indefinitely. By adjusting
> the Ampex's tape speed (and perhaps, I'm not certain of this, the
> Tandberg's head speed) the required results were acheived. It
> did work (if after a fashion) and was used occasionally and was
> an exclusive selling point for Gotham at the time.
> I think the reason a Tandberg was used was because of its
> excellent audio and possibly the ease of modifying the head
> arrangement.
> Now that my curiosity has been piqued I'll try to get further
> info from one of the other Gotham engineers with whom I'm
> in intermittent contact who should have more details. If I learn
> anything additional, I'll post it here. Jack D.


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