I often wonder what the earliest music must have sounded like. I assume it had a strong beat and the melody from a flute or whatever was less important than it is today
The first nations people of Australia seem to have a continuous culture extending back at least 65,000 years. Their songlines are a form of oral history documented in dance formations and storytelling. Remarkably, they include a narrative of the end of the last major ice-age about 12,000 years ago, when sea levels rose by several hundred feet as ice sheets melted. The shoreline swallowed large tracts of land, and allowed the Great Barrier Reef to form. In North America the Great Lakes formed at this time from the remnant fresh water from melting glaciers. This period marked the first cultivation of plants by humans.
Most likely the earliest musical instruments go back at least 40,000 years and included two clapsticks beaten together, plus hollowed out tree branches - the didgeridoo. Ants do a good job of hollowing gum tree branches.
Didgeridoo players can breathe continuously into the instrument while 'talking' to create an incredible variety of sounds. Clapsticks (hundreds of them) and didgeridoo featured in the opening work of the refurbished Sydney Opera House, in "Of the Earth" by Willian Barton. I cannot conceive how music for the didgeridoo can be written down!
Unfortunately archeological evidence of very early instruments may be restricted to rock paintings, as the instruments were made of perishable materials.