The earliest evidence of gamelan instruments and musical traditions dates back to the 8th century, as depicted in reliefs found in the Borobudur temple in Central Java, Indonesia. These inscriptions showcase various musicians playing tuned bronze gongs, which are integral to gamelan ensembles.
Therefore, it is safe to say that gamelan music has been practiced and developed for over a millennium, with its roots stretching back to the ancient cultures of the Indonesian archipelago.