Ask someone to name a 20th-century Japanese composer and they will probably answer Toru Takemitsu.

Ask someone to name two or three 20th-century Japanese composers? They will probably answer with an awkward silence. This isn't because Takemitsu was the only composer writing interesting music in Japan during the last century. According to conductor Ilan Volkov, it's because of what he calls "the Western propensity to pick and champion".

"When it comes to music from exotic countries, we have a tendency to latch on to single figures and not bother investigating the rest," says Volkov. "Takemitsu is the only Japanese composer who is talked about by mainstream programmers in the UK. In fact, Takemitsu often seems to represent the whole of Asia. Don't get me wrong: I'm a huge fan of his music. But I'm also interested in the rest."

Volkov's point is that although UK concert programmers have access to an overwhelming amount of music from around the globe - more music than ever before - their funding pressures mean that they gravitate towards the known factors, the safe bets, and are increasingly reluctant to take risks. The result is that the history of music is simplified to make it bite-sized and digestible; we negotiate the inundation of musical information by reverting to that propensity to pick and champion.

Takemitsu's music has been widely performed in the UK for decades, and for good reason. It has had significant champions among contemporary music circles, particularly the composer and conductor Oliver Knussen. That Takemitsu wrote music for more than 100 films broadens his appeal, as does the fact that his soundworld shares certain sensibilities with French composers such as Debussy and Messiaen. (Volkov admits that he used to think of Takemitsu as "just an advanced Debussy; then I realised that he's one of the most advanced orchestrators ever, and often using the simplest means.")

There is also something ineffably non-Western about Takemitsu's music. His sense of space, his silences, his stillness, his non-linear poise and balance. The way that he can capture everyday elements of the natural world - something as simple as pattering rain or the wind in the trees - not through writing literal or cheesy sound descriptions, but through distilling their very essence.

Tomorrow Volkov conducts the BBC Scottish Symphony Orchestra in a programme that pairs Takemitsu's music with that of his contemporary Hungarian composer Gyorgy Ligeti. The concert is part of The Rest Is Noise series at London's Southbank Centre, and picks up on how the forms and values of these two singular post-war composers reflected the changing societies in which they lived. It's a rich comparison, certainly, but perhaps even more interesting is the programme that happens back in Glasgow two nights later. Here Volkov and the BBC SSO return to City Halls for a concert setting Takemitsu's John Cage-influenced music - including the 1962 Corona For Strings, in which every player is decked out with sheets of coloured plastic and concentric circles that determine what notes they will play - in the context of his fellow Japanese experimental avant-gardists.

The most important of these is Toshi Ichiyanagi. He's probably best known as Yoko Ono's first husband: the two met and married as students in New York in the 1950s, when he was a disciple of Cage and she was a fledging experimental artist. Ichiyanagi returned to Japan in the early 1960s and acted as a kind of ambassador of Cage's chance music, creating a major impact on Tokyo's contemporary arts scene. (The influence went both ways, of course; Cage's encounters with Japanese Zen philosophy ultimately led to landmark works such as 4'33.)

Ichiyanagi returned to Japan after a decade in New York and found a community of Tokyo artists who were not only open to Cagean ideas, but already busy pursuing their own lines of sonic experimentation. The Jikken-Kobo Experimental Workshop had been established in 1951: the same year that WDR Cologne Radio built its famous studio that would come to shape Karlheinz Stockhausen's electronic music. Volkov says that pieces such as Ichiyanagi's Parallel Music - a nine-minute work for magnetic tape that will be played on Saturday - show the depths of what Japanese composers were doing in the 1950s and 1960s.

"Their experiments were every bit as sophisticated as Stockhausen's," he says, "but we just don't know about them. Some of these works are classics of the 1960s, but they are rarely performed outside of Japan. Even in Japan they are not really known. Orchestras there are pretty traditional and don't give much space to programming Japanese music. It's a real loss considering their heritage is so rich."

Scratch the surface and there's masses to discover. In 1960 a group of Tokyo music students formed an improvisational ensemble called Ongaku and made their debut using kitchen utensils, vacuum cleaners and shortwave radios to create an intricate improvised cacophony in an event they called Dance & Music: Their Improvisational Conjunction. In 1962, Tokyo hosted an Exhibition of World Graphic Scores that presented works by Fluxus artists such as Dick Higgins and La Monte Young. Cage and the pianist David Tudor were regular visitors at Tokyo happenings alongside Ichiyanagi and Ono.

One of the most significant performers at such happenings - and a composer whose music also features in the BBC SSO's programme on Saturday - was Yuji Takahashi. As a young pianist he'd been spotted by the Greek composer Iannis Xenakis and became among the first to master the revolutionary techniques needed to perform new graphic scores. Volkov considers Takahashi to be as important a performer of this music as David Tudor. "Why is it," he asks, "that we still know so much less about him?"

One reason that Volkov is keen to explore the major works of Japanese experimentalism is its connection with the likes of Cage. "This is an opportunity to try this music with an orchestra that has already done a lot of American experimentalism, and is totally up to speed with the techniques needed to play graphic scores. That's extremely rare in a symphony orchestra."

But as one of the most open-eared and cross-genre conductors in the business, Volkov also feels drawn to the underground, to music born and performed outside of formal concert halls. He says he's found "an amazing scene" of new experimental music in Japan - "one of the liveliest I've come across anywhere in the world" - and that it's in the tiny, dark bars of Tokyo's underground that composers such as Ichiyanagi and Takahashi are best appreciated today. "Ichayanagi is in his 80s now and he's still working with a lot of improvisers. His horizons have remained broad in a way that I find totally inspiring."

Ilan Volkov conducts the BBC Scottish Symphony Orchestra at London's Southbank Centre tomorrow and Glasgow's City Halls on Saturday.