Following the introduction of Buddhism to Japan, the first detailed reference to its music is an edict of 720 ce, which sought to regulate text chanting according to that of the Tang monk Daorong. In China, new forms of Buddhist chant had developed, as Buddhist texts in Sanskrit were translated into Chinese; further modifications arose with their rendition in Japanese pronunciation. The Japanese term shōmyō renders Chinese shengming, which translates Sanskrit śabda-vidyā, referring to Brahmin priests' study of vocal sound with regard to the chanting of Vedic texts. By the early 13th century, however, shōmyō had become the customary general term in Japan for Buddhist chant (replacing the older term bonbai). Another name, frequently seen in the titles of shōmyō collections, is gyosan.
In 752, at the Eye-Opening Ceremony for the Great Buddha at the Kegon monastery of Tōdaiji in Nara, some 10,000 monks from the various Nara schools participated; but after the removal of the capital to Heian (Kyoto) in 794, the old Nara chant was gradually superseded by those of the Tendai and Shingon schools. In particular, the third head of Tendai, Ennin (794–864), brought back from China much knowledge of Chinese practice, especially in Tantric ritual, and introduced these at the Tendai headquarters on Hieizan. After him Enchin (814–91), nephew of Kūkai (774–835), the founder of Shingon, introduced new teachings and a new style of shōmyō, the Jimon-ryū, at the nearby Tendai monastery of Onjōji. Meanwhile Tōji, the main Shingon monastery in Kyoto, was already a separate ritual centre, and influence on Shingon shōmyō practice and theory was exerted by Kanchō (938–98), grandson of Emperor Uda. Interchange with the Nara schools cannot be documented after 980, and after that Tendai and Shingon increasingly followed their own paths. After the rebuilding of Tōdaiji (destroyed in the civil wars of the 12th century) Shingon and Tendai shōmyō were the basis for new Nara styles. These are preserved most distinctively in the lengthy Shuni-e or o-mizutori ceremony at Tōdaiji, with its vigorous chanting to sweep away defilements of the old year and usher in peace for the new one.
The 13th and 14th centuries saw many changes to shōmyō, as the centre of government moved to Kamakura in eastern Japan. The new Nara styles found favour there, and at Shōmyōji in Kanazawa, Kenna (1261–1338) won support for a combination of Shin-ryū and Myōnon'in-ryū, the two leading schools of Shingon and Tendai respectively. Meanwhile, Zen Buddhism was being introduced at Kamakura, and Pure Land schools such as Jōdo-shū and Jōdo shinshū, as well as Nichiren-shū, were developing individual styles. There was also renewed influence from court song and from various kinds of popular music. These cross-currents both affected the chant and led to new musical forms.
In western Japan, a major conclave at Ninnaji, Kyoto, in about 1145 is said to have recognized four distinct schools of Shingon shōmyō; earlier, Ryōnin (1073–1132) unified the various lineages of Tendai shōmyō from his ritual centre at Raigō-in, Ōhara, north of Kyoto, in 1109. Further reforms of Tendai shōmyō were due to Fujiwara no Moronaga (1138–92), the founder of Myōnon'in-ryū and an expert on gagaku; and to Tanchi (1163–?1237), who founded Shin-ryū (‘New School’) in opposition to the Koryū (‘Old School’) of Jōshin (fl late 12th–early 13th centuries). (The name Shin-ryū of Shingon is written with a different first character.) Tanchi introduced a precise musical theory based on that for gagaku, with rules for modulation, rhythm and pitch, as well as a new five-tone notation system (goin-bakase), which made it possible to perform shōmyō and gagaku together. This last inspired later goin-bakase systems in both Tendai and Shingon, though the simpler meyasu-bakase has continued in use. Tanchi's Shin-ryū completely superseded Koryū in the Ōhara tradition, and from the 14th century there were no major developments. However, the practice and transmission of Tendai shōmyō were gravely affected by recurrent armed confrontations between Onjōji and Enryakuji (the main monastery on Hieizan) and by the destruction of Enryakuji and other Tendai establishments in 1571 by the warlord Oda Nobunaga (1534–82).
Shingon was spared this extreme fate. The Ninnaji conclave, converted by Kakushō (1129–69), had recognized Honsōō-in-ryū, Shinsōō-in-ryū, Daigo-ryū and Shin-ryū, of which the two former, practised at Ninnaji, derived their lineage from Kanchō; Daigo-ryū, practised at Daigoji, derived from Kanchō's fellow-pupil Genkō (911–95), with contributions also from Ninkai (955–1046), while Shin-ryū was credited to Shūkan (Daishin Shōnin, 12th century) by his pupil Kanken (mid-12th century). Shūkan himself had studied both the Ninnaji and Daigoji lines, and his style was supposedly introduced to Kōyasan (the spiritual centre of Shingon) between 1232 and 1237 by Shōshin (dates unknown). Another theory links the transcription of Kōyasan shōmyō to Ryūnen (b 1258) and the Nara monastery Saidaiji (by then affiliated with Shingon). Whatever the truth of the matter, in the 16th century the Daigoji and Saidaiji lineages disappeared, and in succeeding centuries the Ninnaji tradition also died out, so that, despite losses in the 17th century, the Shin-ryū of Kōyasan, usually known as Nanzan Shin-ryū, came to be dominant. Such older Shingon types, especially Shin-ryū, came to be labelled Kogi Shingon-ryū, while newer types, especially Buzan-ha (at Hasedera, outside Osaka) and Chizan-ha (at Chishaku-in, Kyoto), are called Shingi Shingon-ryū.
The less rigid rituals of the Pure Land schools also changed in later centuries and adopted elements of Ōhara school chant, alongside more popular types of religious song, while in the 17th century Ōbaku Zen introduced its own distinctive style, accompanied by loud percussion (fig.25). Buddhism and its music suffered greatly after 1868, but a revival and reconstruction of Tendai chant was led by Yoshida Tsunezō (1872–1957) and Taki Dōnin (1890–1949). In Shingon the leaders were Yuga Kyōnyo (1847–1928) and Iwahara Taishin (1883–1965). Today, through public performances, recordings and studies the future of shōmyō seems assured.
Shōmyō pieces may be classified according to the doctrinal affiliation and rituals they represent; the nature (and language) of the text; modal and tonal structure; and rhythmic type. Thus, particular types of chant serve to expound the teaching (e.g. kōshiki), for praise and lamentation (sandan), intercession (kigan and ekō), confession (sange), offertory (kuyō), catechism (rongi) etc. There are also hymns, in Sanskrit (bonsan), Chinese (kansan) or Japanese (wasan). The invention of wasan is credited to Ennin, and of kōshiki to Genshin (Eshin Sōzu, 942–1017), who himself composed many wasan. Both types remained important across several schools of Japanese Buddhism. Older treatises on shōmyō devote much attention to temperament (onritsu) in relation to Chinese theory (especially the ritsu-ryo scale classification), one influential text being Shittanzō by the Tendai master Annen (841–84). Actual practice has tended to be less fixed, and more important in the tonal structures of shōmyō, and indeed of all traditional Japanese music, are the senritsukei, short melodic units that are strung together in chains and are identified with individual names. Rhythmically, most shōmyō pieces are in free time (jokyoku), but a few have fixed metre (teikyoku) or combine both (gukyoku).