Ever since Sebastiaan (Bas) Ammerlaan begged his parents for violin lessons when he was four, music took a strong hold on him. He started singing when he joined the University College Roosevelt university choir as part of his minor in viola playing. He now studies classical singing at the HKU Utrecht Conservatory, first with Jón Þorsteinsson and since 2016 with Selma Harkink. He also received lessons from David Wilson-Johnson, Jasper Schweppe, Irene Verburg, Kaspar Kröner, Marjan Kuiper and Elisabeth Blom.
Sebastiaan 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 was an intern with the choir of the Dutch National Opera and 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 music.