[1] A lifelong member of Fianna Fáil, he was particularly noted for his work as a trustee and president of Comhaltas Ceoltóirí Éireann.
He was educated locally and won a scholarship to Coláiste Connacht in Tourmakeady, County Mayo, where he qualified as a múinteoir taistil (a travelling teacher of Irish).
[2] Whilst teaching an Irish-language summer Course in Tourmakeady, he met Brid O'Hara, from Tourlestrane, in County Sligo.
In 1951, de Brún was one of the early members of Comhaltas Ceoltóirí Éireann (CCE), a voluntary organisation dedicated to the promotion of the music, song, dance and language of Ireland, which were then in decline.
A member of the national council of Oireachtas na Gaeilge (an annually held festival of Irish culture), he adjudicated at music competitions and was recognised as an authority on sean nós singing.