Siân was born in the village of Deiniolen near Caernarfon, and first came to prominence on the Eisteddfod stage. She completed her music training at the Royal Northern College of Music, Manchester. Siân performed with The D’oyly Carte Opera Company and Opera North where she performed a range of operatic roles. She now concentrates on her Oratorio and concert work. She also works as a voice tutor at the William Mathias Music Centre and as a Peripatetic tutor for Conwy Borough Council. At the 2017 National Eisteddfod, Sian was honoured by the Gorsedd of the Bards for outstanding contribution to music in Wales.