Siegfried Apitz, Dipl.-Ing.
Siegfried Herbert Apitz, co-inventor of the Schaub-Lorenz Music Center,
recalls his involvement in the design and development of that unique, multitrack tape recorder in
the mid-1960s, and other inventions.
Apitz ± 1963
in the Development department
at Standard Elektrik Lorenz, Altena, Westphalia,
PKS: Do you remember much about the time when you helped
develop the BBG [ed. the Schaub-Lorenz Music
Center] at the Graetz company, in Altena,
SA: That was a long, long time ago. While we were still developing the
Music Center at Graetz, the company was taken over by Standard Elektrik Lorenz (SEL). Much later,
SEL became part of Nokia. I no longer have anything about this machine in my possession; I haven't
even got one of those machines anymore.
PKS: I have three of your 5001 Music Centers in
SA: Ha, ha, ha! [laughs heartily].
PKS: I am also very interested in the 5005 model,
the one which contained a record player, radio and a tape recorder in a cabinet. Do you remember
SA: Wait a minute…oh, yes, you mean the 'huge box'!
PKS: In England, we call it the 'radiogram'
SA: Ha, ha, ha!!" [laughs].
PKS: Can you tell me why was the 5005
('radiogram') model not made for stereo reproduction?
SA: Stereo reception in Europe was in its infancy in the early 1960s;
there was not much stereo available back then. So it seemed to us that a 'mono' version of the
Music Center to be more appropriate for Europe. However, in the US they already had FM radio
transmission, so a 'stereo' version was more appropriate there. The stereo version required a
bigger cabinet to house the speakers , and the size of the product was more
acceptable to American consumers.
PKS: While carrying out
research for my website, I found very little about your Music Center written in English, except a
few US and Dutch patent applications. Many documents, mainly German or Dutch, had to be translated.
I believe your story as one of the co-inventors of this tape recorder needs to be told, so I was
hoping you could help me write that story so I can place it on my website.
SA: Oh, oh, oh, ooh, oooh! [groaning regretfully]. I'm not going to be
a big help on this because all this took place in a former life, long, long, long ago. Since then,
I've developed many products such as the VPS (Video Programming System) for ITT Nokia.
PKS: Siegfried, please just remind me what exactly "VPS" is and what it
This invention was used to control the start and stop activities of
programmed timer recordings in video cassette recorders (VCRs) . VPS uses
hidden codes transmitted on Line 16 of a TV signal to start and stop video recordings.
The VCR's decoder filters this coded signal and compares it with the data in the VCR's recording
timetable. Consequently, the video recorder will also automatically record delayed or postponed
transmissions of any timer-programmed material.
If, however, the user disables the VPS, the hidden codes in the transmitted TV signals are ignored.
In that event, the start of recording will be based on the start time that the user has programmed.
The VPS system only works with stations which make use of VPS data transmission.
I assume that Standard Elektrik
Lorenz [ed. SEL] patented this
SA: Yes, but the main patent for the VPS system expired in 2006.
Although the system is still in use , licence fees no longer need to be paid
These other inventions of yours are of great interest to
me, so I have made some notes about them. However, let's return to your involvement in the
development of the Music Center.
SA: This old Music Center was developed so long ago; it was in my
Do you remember what problems you had with the
manufacture and/or design of the Music Center?
SA: I think the problem was due to the machine's huge storage
capacity, which made it relatively expensive to produce. The other thing was that we didn't have
the courage to spend more time on it. Not us, the inventors, but the company.
I understand from my research that many machines were
returned to SEL by unhappy retailers because they were faulty or
SA: Mmm, mmm.
How did the team respond to this?
SA: We had lots of stereo equipment [ed. 6000 stereo model]
which we [ed. SEL] sold to an American company. These units/kits or inner tape machines
comprised a record/playback amplifier, pilot-tone amplifier, motor control and tape drive. General
Electric bought these kits from us, and installed their own receivers and power amplifiers, and
made their own cabinets.
Unfortunately, these units had problems with the 'motor control', so I
was posted to the United States to work at General Electric in Decatur, Illinois, to help them sort
out these problems.
What exactly were those problems with the 'motor
SA: In order to rewind the tape, the rewind motor has to be coupled to
the tape drum that supplied the tape during playback. This meant that the rewind motor required
both a very high rewind speed and a soft-start capability.
This wouldn't be a problem today, but given the resources available to us while we were developing
this machine, we only considered a negative temperature coefficient (NTC) resistor in series with
the motor to be suitable for this purpose.
The problem was that the person operating the Music Center had to be able to interrupt the rewind
function at any given time. Consequently, when rewind was restarted, we found that the NTC resistor
had already preheated, therefore making its impedance low. This caused the motor to start too
quickly. Balancing the heating up and the cooling down of that NTC resistor and its mounting,
created many headaches for us.
What else were the 6000 stereo model used
SA: Quite a number of these units were also sent to the Kennedy Space
Center where they were used for recording 'space communications'.
What exactly do you mean by 'space
SA: The people at the Kennedy Space Center were investigating the
possibility of recording space-flight communication such as, for example, the verbal interactions
between astronauts and ground control, and the communication of data from unmanned space vehicles
to ground control. However, they were not very willing to disclose much about their plans, and only
wanted to know what the capabilities were of our recording machine.
My research shows that a container-load of these 6000
stereo chassis came back from the United States, perhaps because they were not needed or
because the market wasn't interested. A number of them ended up in England, Holland and
Germany, and were sold in kit-form for self-assembly. They were apparently quite popular with radio enthusiasts and electrical
engineers, but did not contain a stereo amplifier or stereo tuner as you probably
SA: Ja, ja. They would have had a record/playback amplifier,
pilot-tone amplifier, motor control and a tape drive just like the kits sold to General Electric.
What you have just told me is possible, but I did not know about this story at all - that they came
back and were distributed around Europe. I was busy enough at the time working on more new
Can you think of any other reasons why the Music Center
was not a great success?
SA: Ja. First of all, the tape had a limited capacity. Moreover, you
could not exchange the tape drums, except during repair. The average consumer could not do this
himself, because you need a technical understanding of how to carry out readjustments.
Then came the introduction of the cassette tape by the Philips company in 1963.
OK, this confirms my research. Incidentally, I am
curious to know what you were holding in your hands in the photo you sent
me? [see photo at end]
SA: That tiny beast is an early example of our later enemy: an audio
PKS: Aaah, yes, I thought it might be.
Siegfried, you were a very interesting and prolific inventor. Based on my research, you have some
65 patents with your name on them.
SA: Ja, ja. Inventions took up much of my time, including weekends and
holidays; I was busy all the time. As time went by, I had to somehow erase a lot of information
from my brain about earlier inventions in order to create enough space, you know, for ensuring that
the products that were developed from those inventions performed in accordance with their patented
Did you ever write anything about your life as an
inventor, or any articles for the companies you worked for?
SA: No, no...
My guess is that you've been retired for four years
SA: Oh, no, a little bit more. Wait a minute. I retired when I was 64,
and was born in 1933, so I am 75 years old now [ed. retired
Were you born in the town that you are speaking from
SA: No, I was born in Berlin. The place where I live now is close to
Pforzheim, where I lived and worked until my retirement. I am now living in Schömberg, Germany,
which is 17 km south of Pforzheim.
Am I right in thinking that the Music Center was
manufactured in Pforzheim?
SA: The Music Center was first manufactured at Graetz in Altena,
Westphalia. That was the beginning, and where the main development of the Music Center took place.
Later on, it was manufactured in Rastatt [ed. 47 km south west of Pforzheim], I
During the time I was in the United States to sort out the problems at General Electric, the
company (including the design and development team) moved from Altena to Pforzheim , and the
manufacturing department to Rastatt.
I was out there [ed. US] for about a year or so (1966-1967). When I returned from the
States with my family, we moved house from Altena to Pforzheim.
You worked together with Friedrich Knochenhauer, didn't
SA: Friedrich Knochenhauer? Ja, ja...
He was an inventor like you, and a colleague, I
SA: Yes, but he was my boss when I joined Graetz KG in
My research suggests that he was the main driving force
behind the development of the Music Center and was its principal inventor. Is that
SA: Ja, but I cannot be absolutely sure.
OK, no problem I will return to him later. Do you know
why the development team chose a track duration of 22 minutes for the tape recorder? Was it
because a single record in those days lasted 3 minutes and therefore you wanted to enable
users to record 7 singles per track?
SA: The reason was simply to get a tape thickness which could somehow
handle the high rewind speed for the short rewind times we were aiming for. So, at the time, the
track duration [ed. one tape run] was not really calculated as a goal of the whole
The Music Center was a compact design. We made many measurements trying out different tape speeds.
OK, the machines had to run at the same speed, but we were not tied to one particular speed,
because there were no exchangeable parts, by which I mean that you could not exchange one machine's
components and install them in another.
We just went for what we assumed would be the best compromise between reserve in frequency
response, rewind time, tape thickness, tape durability and drum dimensions.
One of my website contributors has a 5001 Music Center.
He removed one of its pulleys to slow down the tape speed and managed to extend track
duration from twenty-two minutes to thirty minutes so he could record half-hour radio
programmes . Twenty-two minutes seems a strange track
duration, especially as radio programmes  tended to be around 30 mins long, don't you
SA: Ja. Using a pulley to slow down the tape speed to give a track
duration of thirty minutes was within the performance range we were aiming for with our machine.
However, the tape and the tape heads also had to be designed at the same time during the Music
Center's development, and we did not want to risk any performance loss resulting from trying to
achieve a longer playback time per track.
Only afterwards, when the final production model was completed and tested, were we able to
determine that there would have been no performance loss resulting from reducing the tape speed. We
had deliberately built in a lot of 'reserve' at the outset, by which I mean frequency response.
We didn't push the equipment to its limits, so in hindsight, a thirty-minute cycle would not have
been a problem.
I can imagine that you had other considerations that
were more important than the track duration?
SA: Ja, ja. Another was the thickness of the tape. We also used
different thicknesses, and eventually found an ideal combination of durability and storage
Were the black tapes better than the brown
SA: Yes. The brown Fe tapes had a smoother consistency, but were less
temperature resilient than the black (dark) Cr tapes. The same applied to both the carrier material
and the tape's coating. The 'smoother tape (Fe) offered several advantages over the black Cr tapes.
Brown Fe tapes achieved an optimum tape-to-head contact whereas black Cr tapes had a very long time
Although head wear was lower with Fe tapes, head soiling was higher with Fe tapes. If the tape
surface is soft, the tape-to-head contact could result in tape particles being removed from the
tape and deposited on the surface of the tape head. A thin deposit would increase the gap between
the surface of the tape and the head, resulting in a loss in performance, particularly recording
I guess this also happens when using audio cassette
SA: Ja, the same thing happens when you record
over and over again on a cassette tape. Magnetic material gets scrapped off the surface of the
magnetic recording tape, depositing a thin magnetic layer on the recording/playback heads, causing
similar problems during recording/playback.
One theory is that the inventors may have had
'autoreverse' in mind when they were developing the Music Center. This theory arose because the tape-run indicator's left scale is printed
0-22 minutes from top to bottom and its right scale from 0-22 minutes from bottom to
The theory goes that after recording music on say track A1, the tape unit would
automatically switch to track A2 and seamlessly continue recording, alternating the take-up drum
used every 22 minutes, for up to 46 hours. Had autoreversebeen on your
SA: No, no. The reason why the tape-run indicator scale was printed in
both directions was that it was supposed to indicate the number of minutes of recording time so far
(left scale) and the remaining minutes of recording time (right scale).
We also thought that having two separate scales would offer users a
simple, visual representation of how much recording/playback time had elapsed, so you wouldn't have
to bother about subtracting the number of elapsed minutes from 22.
OK. That makes sense. So would 'autoreverse' have been
technically feasible in the Music Center?
SA: No, no. This idea would not
have been possible to achieve with our machine, due to the construction of the head carrier, and
because the components which operate the two tape movements would not have allowed recording in the
Was that because of the tape heads you were
SA: Ja. The type of heads and the construction, as I just mentioned.
Furthermore, the head carrier is constructed in such a way that the two heads (record/play; erase)
hang in a lever which pulls the heads towards the moving tape when the play/record function is operated,
rather than pushes them against the moving tape.
In addition, tiny air bubbles build up between the layers of tape as it is spooling around the
take-up drum during playback or recording (forwards); driving the tape in the opposite direction to
make 'reverse recordings' would have generated too much wow and flutter, and would have impaired
the quality of sound reproduction.
So it never occurred to any members of the team to try
to design the tape to record/playback in both directions?
SA: I don't think so. That was not our intention.
OK. That puts an end to that line of speculation.
I don't expect you remember all your patents, but do you remember one of the main patents
called Tonbandgerät mit einer Mehrzahl von
Tonspuren [ed. Tape recorder with multiple
soundtracks; Main Patent No. 2]?
This was invented by you and Friedrich Knochenhauer, wasn't
The invention seems to involve recording a pilot tone at
a point on the track where recording is stopped. This way, the tape recorder knows where the
end of the recording is on the track during playback, as soon as it detects the recorded
pilot tone. Is that a fair summary?
SA: It's slightly more complicated than that.
Let's suppose that Track 7 contains a recording of 20 mins of
music. Track 7 is of no interest anymore, and so you decide to make a new recording on Track
7, but this time the recording only lasts 15 mins instead of 20 mins.
The pilot tone is always recorded on the tape when recording is stopped, so now when you replay
Track 7, a tape rewind is automatically triggered after 15 mins, as soon as the pilot tone is
detected. In fact, there is still another 5 mins of music left from the former recording on the
tape, located after the recorded pilot tone, between minutes 15 and 20.
So the fact that 5 minutes of music from an earlier
recording never gets played by the Music Center in fact distinguishes itself from its
successor, the audio cassette tape, which as far as I can recall, would play everything, both
the 'new' recording and what was left of the 'old' recording. Is that
SA: Ja. Correct.
Another patent I came across is what I now call Main
Patent No. 1 on my website: Magnetbandgerät zum
pausenlosen bzw. wahlweisen Abspielen von Informationen, insbesondere
Musikstücken [ed. Tape
recorder with continuous and/or selective playback of information, particularly
This patent mentions five inventors of the Music Center,
including yourself and Friedrich Knochenhauer. I recently discovered in Erfurt that Friedrich
Knochenhauer died back in 1973/4.
SA: Ja. He has been dead for a long, long time.
This is most unfortunate because now I will not be able
to talk to him about the Music Center invention or about his life as an inventor-engineer. Do
you know whether he wrote anything about his life, his inventions or his work?
SA: I do not think so...
No. What a pity.
SA: Because his death was relatively sudden, there was no time for him
to sit and reflect on his former life, no time to recall what was important or what people should
know. There was, I think, no time for him...
Do you remember anything about the team of inventors,
for example, how old they were in 1960, and who did what?
SA: Ja. Friedrich Knochenhauer was my boss and the head of the
development team. He was about 50 then, I think. Alexander Boom was FH's boss and the director of
the Graetz company in Altena. Hans-Georg Fuchs and Gunter Löffler were both at least 40 years old,
and I was the youngest member of the team at 27. We were all design and development
What about Kurt Senglaub  - a new name that I came
across in the German document I was given in Erfurt? He was also part of your team, wasn't
he? So do you know why his name does not appear on any of the Music Center
SA: Ja. He also worked with us in the development team in Altena, and
I believe he was responsible for the mechanical design of the Music Center. I don't know why he was
not mentioned as an inventor, you can better ask him.
Could you perhaps tell me about some specific activities
you were involved in while developing the Music Center?
SA: Ja. We were working very closely with the tape manufacturer for
our BBG machine [ed. Music Center]. I was involved in carrying out audio performance and
tape-durability tests. The tape manufacturer would not reveal what the secret ingredients were for
the carrier material or the magnetic coating.
Unable to produce the right kind of tape material ourselves, we finally achieved wonderful results
with both BASF and AGFA tapes. This didn't really bother us since we were busy enough with other
Siegfried, my Music Center does not contain a fan, but
screw holes in the chassis indicate there was an plan to install one. Why was
SA: Aah, ja. The final production version of the Music Center had a
magnetic tape, and so a fan was not necessary. The development team wanted the machine to make as
little noise as possible when running or playing back music/programmes.
Oh, I see. Are you planning to write anything
SA: No, I think it's too late. I don't think I am an important person,
and my life is not worthwhile talking about, nor writing or reading about.
Please allow me to disagree. You are the sole inventor
or co-inventor of an extraordinary number of inventions; they will go unheard of if nothing
is written about them. That would be a shame, wouldn't it?
SA: The things I invented and/or developed to a sufficiently high
level of performance did make me rather happy. Unfortunately, my wife was not so happy about my
preoccupation with my work, which I regarded to be more important than taking holidays or days off,
especially if I could make the user of a product even happier. Even though the user would never
know what I sometimes thought or felt about the product I was developing.
Obviously there were times when I had to deal with negative results, or lack of time, or not being
able to achieve the original goal that had been set for a product. But I don't find anything
unusual about that. After all, that's life. I have no regrets. I did it my way. I had to make a
living, and now I finally have more time to spend with my family.
Herbert Apitz talked to
the website's author
on 21 May 2008 and also corresponded for a while.
© Peter K. Smith 2008
1. The 5005 had 4 speakers; one big one, a medium-sized one and two
2. More commonly known as 'video recorders' in the
3. Three patents are involved here:
DE 11737C2 and DE 3512156C2. These were applied for by Standard
Elektrik Lorenz AG (SEL) in 1985 (pub. 1986) and were the sole invention of Siegfried Apitz. SEL
combined these two patents under European Patent number EP 0256152B1, renaming them
Method for generating a switching signal in a broadcast or video
receiver (pub. 1988).
4. In Germany and Europe.
5. This was in 1967. Date confirmed by Mrs Rapp, FH's
6. Further details on how this was done, see Jim Weir - Lord of The
7. In UK.
8. Since this interview took place, I discovered an article about the
Music Center written in 1965 by Friedrich Knochenhauer (see Journals).
9. For more behind the exclusion from the patents, see the
Interview with Kurt Senglaub.
1. Apitz made the move from Altena to Pforzheim in around 1965.
2. See also Patent No. 3 regarding