Gagaku is the orchestral court-music of Japan, which has a long historical past. It is the oldest still existing traditional music for orchestra in the world.

Its repertoire is divided into two main categories, the Old Music (Kogaku) and the New Music (Shingaku), named after the period of their creation but also their place of origin on the Asian mainland.

Classified as Old Music are all the works anterior to the T’ang dynasty (618-906), or those which are derived from Indian or South-East Asian prototypes.

Under the name of New Music are classified the compositions which were written during and after the T’ang dynasty, as well as the compositions which were inherited from Koma (Korea, Manchuria) and the ancient kingdom of Bokkai (Po-hai, Northeast-China, on the Gulf of Chihli). In this class are also counted the works composed in Japan but inspired by foreign musical models.

Old and New Music are further divided into Music of the Left, (Sagaku or Saho-no-gaku) and Music of the Right (Ugaku or Uho-no-gaku).

The Music of the Left includes music imported from China and known as Togaku (music from T’ang), as well as the music presumed to come from India and Champa (in Indo¬China) and called Rinyugaku (music from Lin-yi). The newly created works in Japan (Shinseigaku) are also considered as Music of the Left. Togaku is the general term for all these types of music.

Gagaku (literally: refined, elegant music) may be purely orchestral (known then as Kangengaku = orchestral music), or an accompaniment for the dance. It is then called Bugaku, i.e. dances with orchestral accompaniment.

The Kangengaku of the Music of the Left uses three traditionally established instrumental groups:

1. Sankan, the three wind-instruments. These are the

Fue (flute), also known as Ryu teki,
(cross flute with seven fingerholes; 40,4 cm long);
Hichiriki (double-reed oboe),
(seven front finger holes, two rear thumbholes; 18 cm long);
Sho (mouth organ)
(with seventeen pipes, of which only fifteen are equipped with free reeds while the others are mute. Total length 50,7 cm).

2. Nigen, the two string-instruments, namely:

Biwa, the four-stringed lute (122 cm long), played with a plectrum;
So (Gakuso), the So-no-koto,
(a long zither with thirteen strings; 188 cm long)
The string instruments are only used for the Kangengaku. In Bugaku (dances with orchestral music) the string instruments should not be used.

3. Sanko, the three percussion instruments:

Taiko, a drum suspended from a stand
(height with stand 138 cm; diameter 55 cm; depth 17 cm);
Shako, a muted bronze gong
(height with stand 84 cm; diameter 17,5 cm);
Kakko, cylindrical drum with two heads, both of which are played. (height with stand 37 cm; drum length 35 cm; diameter 14 cm).

Under the name of Music of the Right are classified the works imported from Korea and Manchuria, as well as new Japanese works composed in this style. The general term for all these works is Komagaku (music from Koma).

The instruments in the Music of the Right are:

Komabue (Koma flute) with six fingerholes.
length 36,5 cm; diameter circa 1 cm, thus one bu (3,03 mm) narrower than the Ryuteki);
Hichiriki as in the Music of the Left;
(The Sho (mouth organ) is omitted in the Music of the Right);
Taiko, as in the Music of the Left;
Shoko, as in the Music of the Left;
San-no-tsuzumi, "third largest" of the hourglass-shaped drums is played on one head only. It was introduced into Japan by the dancer Mimashi in 612.

As a rule, the Music of the Right accompanies only Bugaku. It never appears as Kangen, (i.e. independent orchestral music).

For the Bugaku the classifications are the same as for the Kangengaku, i.e. just as there is a Music of the Left and a Music of the Right, there is also a Dance of the Left (Samai, Saho-no-mai) and a Dance of the Right (U-mai, Uho-no-mai) in Bugaku.

In Bugaku performances, a Dance of the Left and a Dance of the Right, which follow each other, form a Pair of Dances (tsugai-mai). The order of the dances within the pair is fixed. The Dance of the Right named Nasori will follow the Dance of the Left named Ryoo. The main melodic instrument in the Music of the Left is the Hichiriki, which has a piercing tone. The flute (Ryuteki) plays variations of the melody. The mouth organ (Sho) gives to the music its harmonic support.

In the Music of the Right, of which the style is completely different from that of the Music of the Left, the Komabue and the Hichiriki play two independent but similar melodies. The beats of the San-no-tsuzumi follow distinct rhythmic patterns. The lack of a harmonic support from the Sho is one of the characteristics of the Music of the Right.