Margot Kalse is a classical alt-mezzo singer, specializing in early music. Kalse is founder and leader of the Trigon Ensemble of medieval vocal music.

Kalse is also an experienced singing teacher and has been a choir conductor since 2010. She has her own singing school and gives vocal training to choirs. Kalse has conducted baroque opera's and choir projects, and was guest director of the Leiden Ekklesia Schola Cantorum. She is the creator and maker of the Top 40 van de Gouden Eeuw (Dutch Golden Age Top 40).

Trigon, an ensemble of specialists, sings and studies medieval spiritual music directly from the manuscripts. The aim is not to be ‘authentic’, since no one knows exactly what medieval music sounded like. But what we can do is to approach this music from as close-up as possible i.e. in the original sources. That is why Trigon sings and practices from the early notations such as they are found in the manuscripts. Trigon is the name of a specific notation symbol in Gregorian chant, also known as neumes, indicating a lightly produced sound that ascends and then descends. Trigon was the winner of the International Young Artist’s Presentation in Antwerp in 1998. Since then they have been invited to perform at the Festival of Flanders Antwerp, Tongeren and Bruges (BE) and at the Holland Festival of Early Music Utrecht (NL). Trigon have also performed in the Early Music Series of the Warwick Arts Society (UK), in the Network Series of STOOM (NL), at the Day of Early Music in Alden Biezen in Belgium, the Festival for Early Music of Brezice in Slovenia, and many other venues and festivals in the Netherlands and elsewhere. Trigon also sang during the Canto Aperto in St. Trui-den (B) and in the Musica Sacra Festival in Maastricht. For the Prinsenhof museum in Delft (NL), situated in the former Agatha convent, Trigon recorded songs from a manuscript belonging to the convent.