Trautonium II

[Martin Czech]

It was very near to me and so simple: Just look in a book a have, and
it's all there!  (M.Becker, Synth von Gestern II). 

For your inspiration, how does a Trautonium work?

For a single voice machine you have one top oscillator and four
subharmonic branches from that. Ie. divide by 1 to 24. They all have
sawtooth output signals.

{Translation: Instead of using Thyratron tubes one higher frequency
vco will do, Fmax about 200 kHz, sawtooth. It doesn't need have be very
accurate scaling at the top. Then divide by N (digital). Afterwards add
to saw wave, so you get divided sawtooth waves. Perhaps better to divide
by 2,4,6,8.... instead of 1,2,3.... }

These four subharmonics can be mixed. A "free subharmonic" is also used,
because the usuall subharmonics give only minor chords. The additional
subharmonic allows also major.

{Translation: unfortunately the description is not very accurate in
this point.  Must be a simple sync circuit (soft). It should be possible
to figure out what frequency ratio is necessary to get major chords}

Two bandpass filters allow for fixed formant shaping.

{Translation: two state var VCF & mixer will do}

Frequency controll is via "string manual", ie. a constantan (sp?) wound string,
ie. a resitstor can be pressed down to a steel plate, this giving the frequency
control voltage (much like a violin, the composer P. Hindemith, who influenced
the development of the Trautonium and wrote pieces was also violin virtuoso,
that's why. This way, the vco doesn't need to be very exact, you can compensate for
this with your finger. Hitting the right pitch does need some practise, some
of O. Salas tunes seem to be a bit out of tune ;-> it's characteristic for
the instrument/player system. For better orientation there are "keys" above the string,
these keys can be adjusted eg. for C D G A or other perfect intervals.
The string manual is *THE* feature, it makes the Trautonium sounds so unique.

As soon as the string touches the plate, the subharmonic mixture is switched on
{simple vca}, later a AD envelope was added {well, use an ADSR and vca}.

This is the basic operation.

Next there are 4 sets of subharmonic mixtures, instead of only one fixed.

{duplicate divider taps, additional mixer pots, vca for hard switching,
or better interpolate, this is a NEW feature then}

Additional there are two pedals, one (up/down) controlls volume,
the other (sideways) switches between different sets of subharmonic
mixtures. This can mean sound shape, as well as fast octave switch,
depends on the settings.

Sala's instrument is two voice, ie. two string manuals, two top vco,
two divider chains etc. He wired the pedals so that the left controls
upper manual volume, the right controlls lower manual volume (all
up/down action), the sideway action of the left pedal controlls LOWER
manual mixture and the sideway action of the right pedal controlls UPPER
manual mixture. This is no mistake, this crossing enbles you to use two
independend pedals if you play solo manual, but is difficult to play
when both voices are used.

So far we have no "velocity" or "aftertouch". Another of Sala's inventions
is a fluid resistor under the string metall plate. Some mechanic pull out
a metal blade out of a well of glycerine (sp?) if the string metal plate
is pushed. I guess that the shape of the blade is made such that the
best resolution is at the pianissimo end where it is most needed. The
glycerine/blade arrangement is a resistor, it is easy to see how to
influence volume by that {again vca, why not vcf}.

So we can see, that most of the Trautonium indegredients are allreay
there in a decent modular synth (dividers replaced by hard sync).

One question remains: how could we emulate the manual.  How could we do
this with MIDI? Is it possible that MIDI of 1999 can not give the same
performance then a 1935 Trautonium ?

I fear so.


m.c.