Gendai Hōgaku (literally 'contemporary Japanese traditional music') is not a comfortable listen. That is the point. Its composers use Japanese traditional instruments — koto in 13, 17, 20 and 25-string versions, shakuhachi, shamisen, biwa, plus the gagaku winds — but in the compositional language of the twentieth century: atonality, complex meters, aleatoric passages, extended technique, and the sculpting of silence as material. Miki Minoru's Requiem (1981), written for the 30-piece Pro Musica Nipponia ensemble, layers drones and pointillistic percussion patterns that could not have existed in kabuki or gagaku. Takemitsu's November Steps (1967) sets biwa and shakuhachi soloists in direct confrontation with a Western symphony orchestra; the traditional instruments are asked to play not as symbols of Japan, but as fully modern voices capable of the same compositional grammar as anything by Berio or Boulez.

The founding event was the 1964 creation of Nihon Ongaku Shūdan (Pro Musica Nipponia) in Tokyo, led by Miki Minoru (1930-2011) and Nagasawa Katsutoshi (1922-2008). For the first time, contemporary composition for Japanese instruments had a permanent ensemble, a rehearsal schedule, and a commissioning programme — the Western chamber-music institutional model applied to hōgaku. The decisive international moment was 9 November 1967, when Seiji Ozawa conducted the New York Philharmonic in the world premiere of Takemitsu's November Steps at Philharmonic Hall, with Tsuruta Kinshi (biwa) and Yokoyama Katsuya (shakuhachi) as soloists. That night, Japanese traditional instruments were accepted, in Lincoln Center, as the acoustic equals of Western orchestral instruments.

Watch for complex meter and free notation: Pro Musica Nipponia scores routinely use 5/8→7/8→3/4 alternations, and unmeasured passages marked 'continue this figure for approximately N seconds.' Next, hear non-traditional technique: biwa strings stroked with the flesh rather than plucked with the plectrum, shakuhachi bends pushed to microtonal extremes, koto strings bowed with a violin bow. Third, silence as compositional material — Takemitsu's scores prescribe long rests as an integral part of the sound. Fourth, in the Japanese/Western confrontational works, the traditional and Western forces are placed to oppose rather than blend.

Start with Takemitsu's November Steps (1967) — the Ozawa / Toronto Symphony recording with Tsuruta and Yokoyama is the reference. Then Miki Minoru's Requiem (1981), performed by Pro Musica Nipponia themselves. For further listening: Miki's opera Jōruri (1985), Takemitsu's Autumn (1973), Pro Musica Nipponia's 30th-anniversary Distant Festival (1994), and, at the fringe, Yamamoto Hōzan and Sato Masahiko's shakuhachi-jazz Ginkai (1970).

Tsuruta Kinshi (1911-1995), the biwa soloist Takemitsu wrote November Steps for, was 56 at the premiere and had spent much of her career as an anomaly — a woman playing satsuma-biwa, then still a male-dominated tradition. Takemitsu spent two years with Tsuruta and shakuhachi player Yokoyama Katsuya in his Tama home, one instrument-notation problem at a time. Out of those sessions came Takemitsu's characteristic 'perform for approximately N seconds' notation, since standard Western notation simply could not capture what he wanted the biwa to do. Second: Miki Minoru has said he sketched his opera Shizuka and Yoshitsune in English first and then translated back to Japanese — the international stage was his target from the outset.