Elektronic, Barbican Hall, London

Once a byword for the avant-garde, Karlheinz Stockhausen's name nowadays crops up more as an icon of DJ and mixing culture than in the classical circles to which he belongs. His electronic epics, Kontakte and Hymnen, have been the influential pieces, rather than his respected but esoterically complex piano music and works for multiple orchestras. The Barbican's ongoing Elektronic festival mixes a Stockhausen retrospective skewed towards this end of his output, with concerts by Talvin Singh, William Orbit and the former Aphex Twin, and various sound environments and installations. As history, this probably gives Stockhausen an exaggerated place – in comparison, say, to Steve Reich – but it has the direction right.

Hymnen, his biggest icon of all, started the week. This is the two-hour work from the mid-Sixties that sampled radio broadcasts of national anthems, and developed them along with free electronic inventions. Starting like a channel-hopping collage, it squeezes and stretches the time dimension and settles into long, spacious explorations of abstract sound, projected through loudspeakers around the hall. It left an impact all the way from the Beatles' "A Day in the Life" to ambient music and the creative end of club mixes. The performance drew a crowd, overwhelmingly male, that mixed boffins, contemporary classical buffs, and intellectual ravers from several generations.

For many, it will have seemed archaic to sit reverently in rows, without any visual component, and the music could surely take a more contemporary environment. Instead, Professor Stockhausen, as the Barbican has respectfully called him, set up a dedicated sound system in the main hall. It was very directional, but separated out the strands with analytical clarity, and never tempted you to wallow in the antique radio sounds for their own sake. There are still several levels on which to engage with Hymnen, from the conceptual – prophecies of globalisation – and the straightforwardly technical, to the directly musical. As sound, it's obviously dated and often austere: technology has made so many things possible in the meantime. The collage aspects, too, have a real period character, straight from the let-it-all-hang-out age.

But if the first half-hour takes a struggle for listeners to adapt, the main soundscapes and adventures still have an unmistakable power and range, from brilliance and wit, to grandeur, to a sense of hovering above a tiny planet whose frantic activities, so competitive down below, seem all of a piece when you're up there. It's easy to see why Stockhausen's electronic pieces spawned a whole world of academic music studios. Sunday's events included sessions from the Society for the Promotion of New Music (SPNM) that showcased what aspiring successors have to offer, and suggested that that world seems to exist under his shadow even now.

From a sequence of tape-only pieces, all by men (the later session with live instruments included one woman), what stood out was the high level of technical accomplishment. The composers have far better resources to draw upon than Stockhausen did, and it's a shame that they were not allowed to use the main sound system, banished instead to a smaller one in the Pit theatre. Aesthetically, though, most of them seemed stuck in a world of scary and swooning sounds. The main exception, by Dennis Wiehahn, who went to art school rather than music college, made atmospheric chords from street sounds. Maybe the SPNM wasn't offered pieces of a more radical sort, but this session dwelt largely in a contemporary classical subculture, out of touch with the wider digital mainstream.