Allthough it is evident that Fricke disbanded the moog very soon and turned to acoustic instruments, another ‘electronic’ instrument played subsequently an important role in his work. We are talking here about a mellotron-like instrument, the so called ‘choir organ’. It is difficult to identify with absolute certainty what instrument exactly is meant here.

In 'Der Pate des Krautrock' Gerhard Augustin writes:

"Mit Herbert Prasch, einem Münchner Toningenieur, machte Florian Fricke auf einem Mellotronartigen Instrument seine ersten Filmmusiken. Es war ein Gerät, in dem vorproduzierte Tonbandschleifen - Chor-Orgel genannt - über ein Keyboard gespielt bzw. abgerufen wurden und Klänge und Chöre hervorzauberte, die in Werner Herzog einen visionären Abnehmer fanden." (p.236) 

Augustin states that Fricke together with a Munich sound-enigneer, named Herbert Prasch, composed his first filmmusic on a mellotron-like instrument.
Herbert Prasch worked as an sound engineer on four Werner Herzog films: Letzte Worte (1970), Lebenszeichen (1968), Auch Zwerge haben klein angefangen (1970) and Aguirre (1972).  Probably Prasch gave Fricke access to this instrument.

In an article on Amon Düül published in The Wire (1996) we read the following:

Lemmings did, however, introduce a couple of important new players to the group's complex sound tapestry: Alois Gromer (an old boyfriend of Renate's) on sitar, and an American ex-GI and jazz keyboard player called Jimmy Jackson, whose contribution to Lemmings and the three Amon Duul-related records that followed involved him playing an extraordinary church organ that would become a crucial component in defining the group's sound. 'It was a large, ancient Mellotron-type instrument that had been designed by some crazy instrument builder,' Renate explains. 'For every key on the keyboard he had made a tape of that note which had been sung by a real choir. It wasn't sampled or anything.' Chris adds: 'He devised a system where he took about 150 matches and stuck them in the parts of the keyboard that didn't work. He painted these with different colours so he knew which keys he could play. It was the first such instrument in the world and Florian Fricke of Popol Vuh used it for his soundtrack music to [Werner] Herzog's Aguirre: Wrath Of God. It's in a museum now."

This fragment brings Jimmy Jackson into the picture. At the time Fricke lend his moog to Amon Düül II for ‘Wolf City’, it was possibly through this connection that Fricke discovered the ‘choir-organ’. As a guestplayer, Jimmy Jackson plays choir-organ and piano on ‘Wolf City’, an album recorded in july 1972. He plays choir organ on the following tracks: "Surrounded By The Stars", "Green-Bubble-Raincoated-Man", "Jail-House Frog" and "Deutsch Nepal".

We can hear this instrument in "Aguirre I" and "Aguirre II". These tracks are also in the film that was released on december 29, 1972 in Germany. So these recordings were made during the second part of 1972.
How did Fricke’s work for Herzog’s Aguirre come about? In an interview (Keyboards, 1993) Fricke explains:

Keyboards: schon recht früh, nämlich so ab 1972, begann dann deine Zusammenarbeit, mit dem Filmemacher Werner Herzog, eine Kollaboration, die den Namen Popol Vuh auch über den Kreis der blossen Musikkonsumenten weit hinaus bekannt machte. Von ‘Aguirre, der Zorn Gottes’ über ‘Herz aus Glas’, ‘Nosferatu’ bis ‘ Fitzcarraldo’ und ‘Cobra Verde’ hast du die Musik für Herzogs Filme geliefert. Wie begann eigentlich eure Zusammenarbeit?
Florian Fricke: Das hat - wie eigentlich alles im Leben - einen ganz normalen und unmystischen Anfang. Herzog war damals für die Synchronisation von ‘Aguirre’ in Rom und suchte eine passende Musik bei Ennio Morricone und fand sie nicht. Eine gemeinsame Bekannte machte Herzog auf mich aufmerksam. Er rief mich später in München an, und zwei Tage später war ich in Rom und habe mir den Film angesehen. Zurück in München habe ich dann eine Musik dazu angefertigt, die Werner Herzog auf Anhieb gefiel. Seitdem gibt es die Zusammenarbeit. So einfach war das.

From what Herzog says in the book ‘Herzog on Herzog’ (2002), it is clear that Herzog clearly had in mind what kind of music he wanted for his film:
We spent weeks recording the birds and the soundtrack was composed from eight different tracks. There is not a single bird that has not been carefully placed as if in a big choir. For the music, I described to Florian Fricke what I was searching for, something both pathetic and surreal, and what he came up with is not real singing, nor is it completely artificial either. It sits uncomfortably between the two."(p.80)

In order to come close to Herzog’s ideas for the music, Fricke decided to use the ‘choir-organ’, he was acquainted with through Jimmy Jackson and/or Herbert Prasch.
Herzog must have seen this instrument, as he explains in ‘Images at the Horizon’ (1979):
[...] “I’ve always worked very hard to select the music, but, in doing so, I’ve usually worked very closely with my friend Florian Fricke. For example, to create the music that is used in the opening of AGUIRRE we used a very strange instrument which we called a ‘choir-organ’. This instrument has inside it three dozen different tapes running parallel to each other in loops. The first of these tapes has the pitch in fifths, and the next has the whole scale. All these tapes are running at the same time, and there is a keyboard on which you can play them like on a organ so that, when you push one particular key, a certain loop will go on forever and sound just like a human choir but yet, at the same time, very artificial and really quite eerie

In 2008 Michael Peters and I corresponded on the choir organ with John Weinzierl, Klaus Doldinger and Olaf Kübler. Here some relevant quotes:

   John Weinzierl (Amon Düül II):

"Jimmy Jackson was playing on some of our albums as a studio musician, also playing the choir organ for us.It was through us that Florian Fricke, Doldinger and all the others got in touch with this machine. It used to rest in the "Bavaria" Studios, where various artists recorded and people could use it. Obviously someone has pinched it at some time and I don´t know who´s got it now. Anyway the machine is useless nowadays, because it actually was only a very complicated multitracktapemachine, ahead of it’s time then, but redundant now.  The sounds it played, had to be recorded onto it live, so it could be used. It was just 4 big boxes with taperecorders, and 4 sets of keyboards with it."

"Es war ein großes selbstgebautes Melotron. Es hat nie Jimmy Jackson gehört. Es war im Prinzip ein riesiges Tonbandgerät. Jeder Ton war auf einen Bandloop gespielt, der zu klingen begann, sobald die entsprechende Taste gedrückt wurde. Nach einer Weile nutzen sich natürlich die Bänder ab und ich habe selber erlebt, wie dann die Tapeloops neu bespielt wurden. Man brauchte also einen Chor, ein Orchester usw. die dann Ton für Ton sangen oder spielten, was später auf den Loops zu hören war. Die Kiste war ein totaler Eigenbau und existierte lange bevor es Melotrons gab."

   Klaus Doldinger (Passport):

"Es trifft zu, dass der 1971 auf meinem ersten PASSPORT Album spielende Jimmy Jackson auf diesem Wunder Instrument (eine Art Vorläufer zum Mellotron ) spielte. Das Stück hiess NOSTALGIA. Das Instrument stand damals im Bavaria Musikstudio herum und gehörte einem gewissen Herrn Prasch. Näheres hierüber weiss Olaf Kübler."

   Olaf Kübler:

"Die "Chor- Orgel" gehörte einem gewissen Herrn Prasch, ein Ösi, der in München ein Tonstudio hatte. Nachdem der Pleite gemacht hatte, wurde die Chor- Orgel auf nimmer Wiedersehen nach Wien verbracht. Die Orgel hatte 4 Manuale, Streicher, Mandolinen, Chöre und undifferenzierbare Underground Sounds. Das Ding konnte nur Jimmy Jackson bedienen und ich wusste, wie man die "Kisten" zum Laufen brachte."

Danny Fichelscher states that this instrument came from Vienna, and also refers most likely to Herbert Prasch. (See: BBC Documentary 'Krautrock -The Rebirth of Germany)   

   Herbert Prasch

In november 2013 I finally had a short phonecall with Herbert Prasch. He assured me that the choir organ was already in the studio at the time he took it over from sound engineer Clemens Brendel. So Prasch is not the constructcor of ths instrument. He also stated that Fricke's Moog was first installed in his studio. "Nights were very short in these days", he assures me.

   Frank Fiedler

In an e-mail from August 2016 Fiedler writes: "I remember the choir-organ, a crazy machine. Unfortunatelly I never found a photo of it. Heavy duty. It had 88 loops of normal recording-tape, running around a construction of two axes with alu-disks to hold the tapes, splitted in two big boxes. All covered by plywood. All together it was a construction of lets say 100-150 kg plus the keyboard".

From interview in Uncut, june 2019:

"Unfortunately we never took a photo - today it would like crazy. It was 60 or 80 tape loops with a keyboard; two big plywood boxes with all of this machinery in it, and it was very noisy when it was running because of its electric motors. We had to use speakers so you hear the music over the noise."


Jimmy Jackson

What can be traced from Jimmy Jackson and his choir-organ? He played in several german bands like Embryo, Amon Düül, Eddie Taylor, a.o. Haboob, a one-off project co-led by 3 US expatriots living in Germany: keyboardist Jimmy Jackson, drummer George Green and guitarist William Powell, seems to be his first band. He played with Wolfgang Paap and Lothar Meid in a sixties jazz and soul quintet. Together with Thomas Keyserling (flute), Jackson (organ) contributed to the first album by Tangerine Dream ‘Electronic Dream’(1970), but they were not credited in the album.
With Mal Waldron (electric piano), Eberhard Weber (bass, cello), Fred Braceful (drums) he(organ) recorded ‘The Call’(ECM Japo 60001 - 1971). Also in 1971 he contributed on organ on Klaus Doldinger’s Passport (Atlantic ATL 40299). He is also prominent on the album by Utopia (United Artists UAS 29483, 1973).

Did Jackson use this particular instrument on the Haboob-album? For the New Gibraltar Encyclopedia of Progressive Rock ( David Wayne gives the following hint:

"Interesting. The major point of interest for most progressive fans is Haboob's very significant connections with Amon Düül 2. The LP features psychedelic cover art by Amon Düül 2 keyboardist Falk U. Rogner, and it was produced by Amon Düül 2 saxophonist / producer Olaf Kübler. Jimmy Johnson has numerous studio credits, but is perhaps best known in prog-rock circles for his collaboration with Amon Düül 2 on Wolf City and Dance of the Lemmings (along with Phallus Dei, the band's best work, in my opinion). As you'd expect, Johnson's effects-laden organ and Mellotron (here called "choir-organ") are quite prominent. Unfortunately, Johnson's compositions aren't nearly as distinguished - the LP is comprised of a free improvisation (during which Green cuts loose to display some considerable jazz chops), a very Hendrix-inspired blues, and some pretty straightforward psychedelic soul - funk - rock pieces. The end result is sort of like a collaboration between Amon Düül 2 and early Funkadelic, or the Chambers Brothers (or perhaps even Sly Stone), minus the extended guitar explorations. The vocals, guitars and keyboards are heavily processed throughout - in fact the singing is pretty much buried beneath multiple layers of effects and electronic weirdness. The lyrics are only occasionally understandable. Despite the relative simplicity of the music, it has a lot of appeal - and I would urge those of you who are interested in a fusion of Euro-psychedelia with US soul and funk to seek this one out. Green's hard-driving rhythms give the music a real funky edge, and Johnson does some interesting stuff. -- Dave Wayne "

From this it seems fair to conclude that Jackson used this instrument already for his Haboob-project. Did Jackson use this organ later in his career? If I'm not mistaken, the instrument is also used for the track 'Nostalgia' on the first album of Doldingers' Passport.
Andy Thompson’s site on mellotrons - - contains a list of albums that are falsely mentioned as albums with mellotron. For example the Amon Düül-albums that have Jimmy Jackson playing on it:
Amon Düül II are a distinct oddity in the Wonderful World of Mellotron (cough). On at least two of their albums, Jimmy Jackson is credited with 'choir-organ'. What does it sound like? Well, ostensibly like Mellotron choir, but right at the beginning of 1971's Dance of the Lemmings, there's a chord that probably holds for 30 seconds or more, although it doesn't half sound like the classic 8-choir. I've recently been informed that like Kraftwerk, Amon Düül II used an Orchestron, the 'professional' version of Mattel's Optigan (of Steve Hackett fame), which plays optical discs, meaning that notes can be held indefinitely, although another report has it that the 'choir-organ' was a one-off machine, possibly from the '50s, and Jackson was the only person who could get a decent sound out of it. Who knows? I'll be doing more research on the subject, anyway, so more news when (if) I find out anything of use."

Thompson’s mellotron-site recently moved to: He changed the above text into: 
Amon Düül II are a distinct oddity in the Wonderful World of Mellotron (cough). On at least two of their albums, Jimmy Jackson is credited with 'choir-organ'. What does it sound like? Well, ostensibly like Mellotron choir, but right at the beginning of 1971's Dance of the Lemmings, there's a chord that probably holds for 30 seconds or more, although it doesn't 'alf sound like the classic 8-choir. Allegedly, it was a one-off machine, possibly from the '50s, and Jackson was the only person who could get a decent sound out of it; I believe it was far more complex than a Mellotron (!), although very little hard information is available on the subject. It's now supposed to reside in a museum somewhere in Germany. WHERE? For what it's worth, Florian Fricke also used it on various Popol Vuh releases, principally Aguirre: Wrath of God.

Noel Jones writes in a article on ‘Amon Düül II’ for the Record Collector (june 1993): 

"The album ("Dance Of The Lemmings") featured the unique sound of the choir-organ, a 20-year-old hand-made keyboard which sounded like a piercing, violent version of the more commonly-used Mellotron.
Jimmy Jackson was the only person able to play this monstrous machine, and therefore guested on a number of Düül releases. The guitarists were gelling particularly well by this time, both in their complex compositions and their fluid musicianship. It's worth mentioning that much of Amon Düül's more avant-garde work was reminiscent of the early Pink Floyd