Ever since Sebastiaan (Bas) Ammerlaan begged his parents for violin lessons when he was four, music took a strong hold of him. He started singing when he joined the University College Roosevelt university choir as part of his minor in viola playing. He also studied musicology there. From 2013 on he studied classical singing at the HKU Utrecht Conservatory, first with Jón Þorsteinsson and from 2016–2020 with Selma Harkink.
Since 2020 he follows the master Ensemble singing at the Royal Conservatory with Harry van Berne (ensemble) and Gerda van Zelm (solo singing). He also received lessons from David Wilson-Johnson, Jasper Schweppe, Irene Verburg, Kaspar Kröner, Marjan Kuiper and Elisabeth Blom.
Sebastiaan sings in the Bach Choir of the Netherlands and NKK NXT, and sang with Meesters & Gezellen (2016–2018), the Dutch National Opera Academy, Muziektheater Hollands Diep, the National Youth Choir, TENSO Europe Chamber Choir and the Zed Chamber Choir.
In 2017, he founded the Ensemble for New Music with soprano Veronika Akhmetchina. He also sings in Ensemble Cantorex with soprano Iris Bouman, alto Hester Westra and tenor Dierick Aartsen, a vocal ensemble specialising in Renaissance and Baroque music.