A new column that spotlights interesting and rare recording equipment from the past.

The Tempophon

The Tempophon manufactured by Eltro in Germany is, as the name suggests, a tempo machine, or to be more precise, a tempo and pitch adjustment machine. Tempophons are as rare as their latterday electronic counterparts are expensive, so at less than one hundred pounds, a good example is a real bargain.

The unit enables the easy adjustment of both tempo and pitch, but there are snags. Firstly, it is a tape playback unit and therefore it cannot operate in real time. Secondly, it must be used in conjunction with a 15ips tape recorder. These restrictions limit its use to the studio, whereas the modem electronic transposers are able to function in both the performing and recording roles. Even if the Tempophon could work in real time, its 55lb weight would preclude its use on stage.

The machine, a fine example of the precision engineers art, is built around a substantial top plate and houses the heavy motor, flywheel and vari-speed assemblies. The vari-speed arrangements serve to alter the actual tape speed via the capstan and the relative tape to head speed by means of a rotating 4 head, head drum.

Operation

The operating principle is that the tape (recorded at 15ips) travels left to right, whilst the head travels right to left. If the head travelled at 15ips also everything would be reproduced at twice the frequency and of course in half of the time. That is how it would be if the head actually moved along the tape. But by virtue of its rotation, the playback head only travels a little way along the tape before being replaced by another head starting a little further back. The effect is to produce an invisibly 'spliced' tape as minute portions of the original are sampled and reproduced so as to produce the contracted or extended version.

The adjustment of actual and relative tape/head speeds permits a time variation of one half to double duration without pitch change, or alternatively a pitch variation of 7 half tones up or down without time change; various combinations of the two are possible.

The pitch shifting facility enables the production of harmonies and other effects, whilst time compression allows the production of complex rhythms at a rate consistent with skill, which may then be brought up to speed. Comic sound effects are also possible, though few people seem inspired to include humour as an ingredient in their artistic efforts.

The Tempophon is indeed a recording industry rarity, but the chances of buying one which may be around remain high. Because so few people know what it is and what it does, they will probably just pass it by without a second glance.