A year after war ended, the local radio station was given a symphony orchestra. And, as its current boss Heiner Muller-Adolphi explains, this orchestra saw its prime job as administering cultural first-aid. "People desperately wanted to hear the music they had missed during the Nazi regime. Schoenberg and Webern and Bartok and jazz - all the things which had been proscribed as decadent. They felt completely cut off from international musical life." When the new radio building was opened in 1953, Stravinsky marked the occasion by conducting the first German performance of his opera Oedipus Rex. A year later, the radio station spawned a baroque ensemble.
It also gave birth to something with bigger repercussions. Tape recorders had been pioneered by German radio, but it was the Frenchman Pierre Schaeffer who in 1948 first used one to produce that collage of "found" sounds known as musique concrete. In 1951 Cologne Radio went one better and founded the electronic studio where Karlheinz Stockhausen launched the experimental odyssey on which he is still engaged today. His Gesang der Junglinge - in which the recording of a boy singing the Benedicite was spliced with electronically generated sound - represented music's boldest leap since Schoenberg.
As Stockhausen got into his stride, composers like the Romanian Iannis Xenakis and the Italian Luigi Nono joined in. Meanwhile Hans Werner Henze and the Argentinian Mauricio Kagel came to stay - and also, with Stockhausen, to teach at the new conservatoire. Students who caught the virus of experimentalism stayed on as professional performers; thanks to the avant-garde policies of the radio orchestra, they found a ready-made public. Thus did Cologne become the new-music capital of the world. Even today, Stockhausen (putting quartets in helicopters), Henze (reverting to romanticism) and the increasingly Dadaist Kagel are local eminences grises, while their students roam performance-art's wilder shores.
Cologne's cathedral precinct bristles with music shops, in several of which a book entitled Music Law is prominently displayed. This is significant: musicians in Germany's 120 state orchestras have rights that are the envy of musicians elsewhere. They earn over pounds 40,000 a year, and are all on life-contracts. They can go in at 21, and retire 44 years later after a stress-free career (there seem to be no tales in Cologne to match London's horror stories of second violinists devouring beta-blockers before they play).
But, as all the world knows, Germany's economic miracle is on the point of collapse, and the orchestral good life is suddenly under threat. A straw poll of key musical figures in Cologne reveals sharp disagreement over the future of these luxurious contracts. Muller-Adolphi says he has long wanted to see three-year contracts - "otherwise people can get lazy, go soft" - but the unions have always vetoed that. "But as cities start to go broke, they will not be able to afford life-contracts any more.
Finally the unions will have to accept this."
Not so, says a senior cellist in his orchestra. "Life-contracts are normal in all German professions, and no conductor or administrator will be able to change it. If you are at the top level of ability, you have the right to be safe in your employment." Yes, age may sometimes reduce physical competence - "but, if you are older, you have more experience, so it balances out." An administrator at another orchestra, despairing at the difficulty of trying to remove tired players, glumly remarks that it would actually be easier to close orchestras down than abolish life-contracts.
Hans Vonk, the laid-back Dutchman who has been principal conductor of the Radio Symphony Orchestra for the past six years, is glad for his players' good fortune - and rates their work high - but thinks a shade more stress might produce even better results. That's as may be, however, because at the end of this season he's off to St Louis - succeeding the charismatic Leonard Slatkin - and his departure is provoking frantic manuvres behind the scenes.
For, as Munich is currently finding - conductorless since the death of Celibidache - there are not enough charismatic conductors to go round. The RSO has appointed a "finding committee" with representatives from the rank and file, and everyone has had the right to make nominations. These have been whittled down to three - Andre Previn, Neeme Jarvi and Semyon Bychkov - each of whom is currently doing concerts which are, in effect, auditions. The contest is all very gentlemanly, and it's all officially denied, but everyone is agog, because much depends on the outcome.
When asked to crystal-gaze 10 years hence, Vonk gives a candid reply: "I see fewer orchestras, less rehearsal time, lower pay, and shorter contracts. Everything will be more difficult." He then adds that he hopes the Radio Symphony "doesn't make the same mistake which the South Bank made in London. I don't want to see them retreat into the safe haven of Beethoven's Fifth and Tchaikovsky's Fifth." He was shocked to be asked, on a recent visit to London, to lop off a "difficult" work by the Cologne avant-gardist Bernd Alois Zimmermann, on the grounds that it might put punters off. (This, presumably, before ENO turned the same composer's Die Soldaten into a hit.) "The orchestra absolutely must preserve their taste for adventure."
This sentiment may be somewhat undercut by the "safe" repertoire they're bringing to Britain this week (Weber, Mendelssohn and Brahms), but it is vigorously echoed by Renate Liesmann, Cologne's leading new- music co-ordinator. "This city has offered a protective biosphere in which composers from all over the world have been able to make their experiments, but this biosphere is now under threat. Our cultural life is getting more and more expensive, and there is less and less scope for inspiration. People won't admit it yet, but everyone can sense that some fundamental change is in the air."
At which point it seems appropriate to seek the view at Cologne's 10- year-old Philharmonie - acoustically one of the best halls in the world. Business, say its bosses, has never been better, and that goes for the avant-garde stuff as well. This spring they are holding their second Musiktriennale, in which the names of Rattle, Barenboim, Kremer and Bjork figure with equal prominence. On two successive nights I find the 2,200-seater hall packed, with long queues for returns.
Music in post-war Cologne has followed a huge arc - rising from the ruins, cruising the heights - but it's not going to crash back down to earth just yet.
Cologne RSO on tour: Sun, Bridgewater Hall, Manchester (0161-907 9000); Mon, RFH, London (0171-960 4242); Tue, Symphony Hall, Birmingham (0121- 212 3333)