Welcome to follower Nam Hoai, a Vietnamese architect with two blogs: nhomthangmuoimot, about 19th and 20th century art from different parts of the world, and nguyenhoainamkts, which covers a miscellany of subjects, including architecture, photography, and music.
One reason for our hero travelling to the Eastern edges of the Empire is to track down a missing hydraulis player. The hydraulis or water organ is said to have been invented by Ctesibius in the 3rd century BC. In Ctesibius’s version, water was used to regulate the flow of air through pipes to produce music from a keyboard, but as time went by the use of bellows became as popular as water. Both versions of the instrument died out in the West after the fall of the Western Empire, but survived in the East. In 757, the Byzantine Emperor Constantine Copronymus presented Pepin the Short, King of the Franks and father of Charlemagne, with a bellows-operated version which was further developed over time to become the church organ as we know it today.
The remains of a hydraulis were found in excavations of Aquincum (modern Budapest) in 1931. The pamphlet guide to the Aquincumi Múzeum in Budapest shows a display of excavated pieces and a modern reconstruction.
Parts of another hydraulis were found at Dion, near Mount Olympus, in 1992. archaeologychannel.org has a rather old page with a radio interview about the hydraulis and a video interview and demonstration. The page does have other links to information, but unfortunately they are all broken. The video dates back to the early days of streaming (the radio interview thoughtfully explains what streaming is) and is rather small and jerky. You can see a rather better video of the hydraulis in action below:
Musica Romana, a modern group specialising in the recreation and performance of Roman music, include an extract from a piece called Aulos et Hydraulis on their myspace page. (except where noted, illustrations in this post come from wikicommons).