Theatrum Instrumentorum was formed in 1985 in Milan with the intention of cultivating a repertoire ranging from the Medieval to the Nineteenth century,  proposing both Western European music and that which flourished within the Byzantine and Ottoman empires, a repertoire always seen in terms of historical-musical research and performance with a constant reference to early sources, integrated at times with the study of archaic but still living non – written musical traditions. Presently, it is acknowledged by both critics and public as one of the finest Italian ensembles in the European early music panorama.
The group, which performs in consort of three to ten members, has participated in many concert events both in Italy and abroad and in several international early music festival (Antwerpen, Arona, Ascona, Basle, Bologna, Cremona, Freiberg, Krakow, Locarno, Milan, Paris, Rome, Regensburg, Strasbourg, Stresa e Lago Maggiore, Venice, Urbino e Pesaro, Warszaw, Zadar a.o.). From 1989 to 1995 the ensemble frequently also worked with other vocal and instrumental groups interested in early repertoires ( Accademia Bizantina, Chiaroscuro, Coro della RTSI, Ensemble Concerto, Ensemble Elyma, Sequentia a.o.).
In 1987 a study group was formed within the ensemble in order to research the repertoire of dance music and the reconstruction of dance practices of the fifteenth and the sixteenth centuries. From 1990 to 1993 and then again in 2004 the ensemble has worked in partnership with the Piccolo Teatro in Milan, performing in four productions.
From 1996 to 2000 Theatrum Instrumentorum recorded for the German recording label ARTS.
The group’s meeting in the mid–nineties with Moni Ovadia marked the beginning of an important  project dedicated to the music of three monotheistic religions with has toured extensively. This concert, Shir del Essalem (Songs for peace), was recorded in March 2002 as a double CD (and in December 2004 as a DVD) and published as a special edition by the Italian leading classical music magazine Amadeus. Renewing the collaboration with Amadeus, the group released (December 2005) a special issue, with double CD, dedicated to the city of Jerusalem.
Theatrum Instrumentorum has also taken part in several radio and TV programs in Italy and abroad.