Hortus Musicus is an Estonian ensemble that was established in 1972 by Andres Mustonen, a violin student of the Tallinn State Conservatory. Hortus Musicus specialises in performing early music, including 8th-15th-century European forms such as Gregorian Chant, Organum, Medieval Liturgic Hymns and Motets, the Franco-Flemish School, and Renaissance Music. The group also presents early, non-European styles including Indian Ragas, Israeli temple songs, Arabian mughams and Jewish music. The group's repertoire has also included pieces by 20th-century composers.
Hortus Musicus has given concerts in the US, Turkey, Japan, and Israel, and has performed at several major early music festivals. They have recorded approximately 35 programmes, a portion of which is available from companies such as Erdenklang, Musica Svecia, Forte and Finlandia Records. The group's latest recording is "Ave...": 'music from the late Middle Ages in memoriam Helle Mustonen'.