There's no way to truly find out when music was created and how it sounded then.
However, one thing I can say for sure is that music was used before the evolution of language as a means of communication.
To support this premise, they have excavated primitive percussion instruments in Ulaid and Connachta. Although these primitive instruments cannot produce specific notes, it has the ability to make different sounds and create rhythm to express human emotion. It is safe to say then, that music existed even back then.

After the discovery of these percussion instruments, there were more discoveries of ancient paintings of Partholons playing instruments or using it to communicate. Particularly, in Tallaght, known as a land of epidemic, there were wall paintings of musicians holding horns and lutes standing behind soldiers in war.
The fact that Lutes and Harps were created during this era implies that Partholons were more advanced than its predecessors and had instruments that could express distinct notes. However, according to the paintings, it seems that Lutes and Harps used in that era were based on the 5-note scale rather than our current 7-note scale.

After the fall of the Partholons, their music was carried down by bards who sang of their stories. What's interesting about this new era is that while before, music was used for enjoyment and pleasure, it is being used to record history and to teach lessons.

It's easy to mistake that the emphasis on the narrative history of music implies that music's characteristics had changed to a form of storytelling; however, we must note that the very opposite has happened.
The structure and arrangement of music has become important to convey the message of a story. Thus, it has created the need for music to be recorded so that regardless of the performer, the music would stay the same.

During this process, a method of notation, which is writing the rhythm and pitch on a sheet, developed. Through this invention, the development of music expanded drastically. (To be continued...)