He was a successful competitor at eisteddfodau for which he adopted the pseudonym Eos Morlais, and in 1867 he won the main prize as a vocalist at the National Eisteddfod of Wales.

At the age of nine he began working in a coal-mine, but due to showing a talent for singing and recitation, he was given lessons in music by an uncle.

He took a course of instruction at the Swansea Training College and was successful enough to give up work to devoted his whole time to music.

Hen Wlad Fy Nhadau was adopted as the Eisteddfod song in 1880 and sung at every Gorsedd ceremony since.

In 1887 Rees was invited to sing at the National Eisteddfod in London in front of the Prince of Wales, Albert Edward.