Seikilos epitaph
The Seikilos epitaph is the oldest surviving complete musical composition, including musical notation, from anywhere in the world. The epitaph has been variously dated, but seems to be either from the 1st or the 2nd century AD. The song, the melody of which is recorded, alongside its lyrics, in the ancient Greek musical notation, was found engraved on a tombstone (a stele) from the Hellenistic town Tralles near present-day Aydın, Turkey, not far from Ephesus. It is a Hellenistic Ionic song in either the Phrygian octave species or Iastian tonos. While older music with notation exists (for example the Hurrian songs), all of it is in fragments; the Seikilos epitaph is unique in that it is a complete, though short, composition.
Tournai Mass
Before the 15th century, most musical settings of the Ordinary of the Mass were grouped according to movement. For instance, the Ivrea Codex and Apt Codex both contain mass movements, and these movements are grouped so that all of the Kyries are together, all of the Glorias are together, and so on. A priest selecting the music for the service would choose one from each group to be sung, and so any setting of a movement could be used in combination with any other. The Tournai Mass is the first known mass to have been written in a manuscript as if it were a single unified setting of the entire Ordinary. Three other similarly compiled masses from the 13th and early 14th century survive: the Toulouse Mass, Barcelona Mass, and Sorbonne Mass (also known as the Besançon Mass). All of these masses are anonymous, and musicological scholarship indicates that all of them are compilations of the works of several composers.