Few vocal groups have ever matched the Harmonists' technical brilliance, innovative arrangements, or the pure joy they distilled into their music. Their trademark sound was harmony singing that was miraculously close, delicate and polished. Although they were classically trained former opera singers, they performed Duke Ellington numbers, German folk songs and popular music of the day, and mimicked instruments so precisely that audiences sometimes mistook them for a chamber orchestra.
They were adored for their sweet, silly love songs, and were as comfortable singing in Spanish, French, English or Italian as in German. They toured extensively, sold hundreds of thousands of records, made seven movies - of which only 12 minutes survive today - and were loved at home and around Europe.
Three of the sextet - the group's founder and principal arranger Harry Frommermann, the Polish-born baritone Roman Cycowski and the second tenor Erich Collin - were Jewish. Initially, the Harmonists' popularity among Nazi officials shielded them from persecution during the early stages of Hitler's rise. Then, in 1935, the Jews were banned from performing. The Harmonists gave an emotional farewell performance in Munich, the three Jewish members went into exile and the band split into two rival groups.
In Germany, the three "Aryan" Harmonists, the pianist Erwin Bootz, the bass Robert Biberti and the top tenor Ari Leschnikoff, evolved into Die Meistersextett, performing a drastically limited repertoire, since jazz and music by black or Jewish composers was forbidden. In 1941, this group was also banned by Nazi officials who had decided that songs about flowerpots or pastiches of Rossini were inimical to the German war effort.
Meanwhile, in Vienna, the Jewish contingent, reformed as the Comedy Harmonists, continued to tour the world and, in the last years before the war, became hugely popular in Australia where, among others, Barry Humphries, the future Dame Edna, heard them on the radio.
"When I think of the Comedy Harmonists I think of myself as a kid in the very early Forties," he says. "I had a small portable wind-up gramophone sitting on a tree stump in the middle of the Australian bush, playing these haunting, very beautiful, sometimes amusing, invariably entertaining songs.
"It was the mood of the songs - there was a jauntiness, a gaiety, and a sort of courage about what the Harmonists did when one considers them in the historical context... `Wochenend und Sonneschein' was their great song, which in English is `Happy Days Are Here Again'. What a terrible irony there is in that."
Today, other admirers of the group include the ex-Talking Head David Byrne and the former Fairport Convention guitarist and songwriter Richard Thompson.
"I suppose I'm a member of one of the smallest cults in the world outside of Germany," says Thompson. "But I'm devoted. Most people I play their music to think the Harmonists are too syrupy or barber-shop or something, but it's fantastic stuff. I really love it and play it a lot.
"They were terrific singers, they had a great blend and they were very original. They started out trying to imitate an American swing group, the Revellers, but they far transcended them and in turn influenced people like the Mills Brothers with their impersonation, not just of instruments, but whole orchestras.
"When you hear them do Duke Ellington or the classics it's extremely amusing and incredibly accomplished at the same time. They were a wonderful mix of the emotional, the sentimental and the serious... I'm sure their sense of harmony influenced me somewhere, though I couldn't say precisely how."
Most of the Harmonists died in relative obscurity. Neither of the successor groups ever matched the perfection of the original band, and the six performers never met again.
The three Jewish members eventually moved to America. Frommermann, the lyric baritone and inspiration of the group, changed his name to Frohman, went back to Germany as an American army officer in 1945, and served as a translator at the Nuremberg war crimes trials. Later he worked as a New York taxi driver, and once spent his meagre earnings on hiring a studio to record a version of "Flight of the Bumblebee" in which he took the part of all the instruments of the orchestra. He eventually returned to Germany, and died in Bremen in 1975.
Collin, who had grown up in an aristocratic Prussian family which had converted from Judaism to Lutheran, died in Los Angeles in 1961. Cycowski, honouring a promise he had made to his father who was murdered by anti- Semitic Poles in Lodz in 1941, became a synagogue cantor in Palm Springs.
Of the non-Jews, Leschnikoff returned to his native Bulgaria and lost his money in the war, though he was briefly feted by a second generation of fans in East Germany towards the end of his life. The amazing Bootz and the dictatorial Biberti, whose name was listed in the Berlin telephone directory alongside the words "Comedian Harmonist" decades after he had ceased to sing, both died in the Eighties.
Yet, nearly 70 years after their heyday, and two months after the death in California of Cycowski at the age of 97, the Comedian Harmonists are enjoying a revival.
In New York, two musicals about the group are headed for Broadway. March sees the opening of Band in Berlin, by Susan Feldman, a show that tells the group's story based on Cycowski's videotaped memoirs. A second show, Harmony, by Barry Manilow, also recounts the band's history, but uses Manilow's music, and is due to open later this year.
Meanwhile, a terrific film about the band, Joseph Vilsmaier's Comedian Harmonists, was Germany's surprise hit movie last year. Sales of EMI's six albums of old Harmonist songs have gone through the roof, and Germany has suddenly been awash with tribute bands - 40 of them at the last count. Vilsmaier's film has gained big audiences all over Europe and opens in America next month, but it has no distributor in England.
Next Thursday, however, the Goethe Institute in London will stage a rare screening of an earlier film, an acclaimed 1976 German TV documentary about the Harmonists by Eberhard Fechner. The evening will also include a lecture and a performance of a handful of the Harmonists' pieces by the vocal group Cantabile.
Cantabile's Michael Steffan, who has carried a torch for the Harmonists for 20 years, is still astonished by the virtuosity of the group's original recordings. Recreating a Harmonist song in Munich recently, he worked with an experienced German session pianist who simply could not believe that the shimmering, understated piano playing of Erwin Bootz was the work of one man, and eventually needed two takes to complete the performance, using four hands where Bootz had used two.
Giora Feidman, the father of modern klezmer music, who appears in Vilsmaier's film, sees spiritual significance in the Harmonists. "I think they were among the greatest musicians of the century. Many people try to imitate them, but they cannot. No other group is so pure in their artistic values. Their music has an absolute spiritual content. They were conscious of the meaning of sound, about the power of sound as a communicator, a healer."
For Barry Humphries, though, the band represents something more poignant: "[They are] the voice of what Germany might have been before the terror. They represent the optimism, the culture and the gaiety of Europe before it committed suicide."