Christopher Morley recalls his meetings in Birmingham with Karlheinz Stockhausen.

Karlheinz Stockhausen was one of the most reviled, most respected and most sensational of 20th century composers. He remains probably the most influential music figure to have been born in that century.

Along with others of his generation – Pierre Boulez and John Cage among them – he developed lines of musical thinking which opened new portals into the way we perceive the art, including electronic music, the use of structured improvisation, the exploration of unconventional sound-sources, the design of graphic scores and, for me the most exciting of all, the invention of “moment-form”.

Here, the music is laid out in little “moments” which can be approached randomly by the performers, just as long as the “moment” which is moved to bears some element of the preceding one, whether dynamics, texture or tessitura. Fascinating and logical. The performance stops when any “moment” is being played for, say, the third time.

But Stockhausen was also notorious for the demands made upon his performers, whether in terms of stamina, such as in ‘Stimmung’, six unaccompanied voices pitching their tones as closely as they can to a series of natural harmonics and coming in at a gruelling hour-plus, or in ‘Aus den sieben Tagen’, where any number of musicians may perform, with the stipulation that they should have fasted beforehand.

There are some fascinatingly quirky pieces in his output, such as ‘Tierkreis’, existing in a variety of combinations (one of them involving musical boxes) and based on the signs of the Zodiac, and ‘Harlekin’ and its little brother ‘Der Kleine Harlekin’, for solo clarinet.

Perhaps Stockhausen is best remembered for the truly gargantuan dimensions of his most spectacular compositions: the three orchestras of ‘Gruppen’ (memorably given in a double performance by a tripartite CBSO in the ICC, Simon Rattle, his mentor John Carewe, and his protégé Daniel Harding conducting); surpassed by the four orchestras and choruses of ‘Carre’; and the week-long operatic cycle ‘Licht’ of which ‘Mittwoch’ is obviously a part, super-Wagnerian in scale but more Miltonian in its context, based on Good against Evil, with Michael (shades of the Archangel, but with reminiscences of Wagner’s Siegfried) the hero on the side of Good.

And one of the most beautiful fruits of Stockhausen’s teeming, outreaching imagination is ‘Sternklang’ (“Star Sound”), described by the composer as “park music for five groups”. The small groups of varying makeup are dotted around the park, with the huge gong so beloved by Stockhausen at the hub.

From here, torch-bearing messengers run from group to group, humming notes and bearing instructions as to their next contribution, and thus the performance progresses, beginning in daylight and coming to an end at last when the full moon rises.

Birmingham’s Cannon Hill Park was the perfect venue for a performance of ‘Sternklang’, on July 14, 1992. The five performing groups, each miked up to two enormous loudspeaker towers and spaced exactly 100 yards apart, were made up of musicians from Birmingham Conservatoire, Birmingham University, Birmingham Contemporary Music Group, Anglia Polytechnic and Midland Arts Centre. And Karlheinz Stockhausen was there to supervise it all.