Tiennet Simonnin made his debut on the chromatic accordion in 1988. As a teenager, he became passionate about Irish music and began learning the Irish repertoire and style, first on the tin whistle, then later on the chromatic accordion, uilleann pipes and bouzouki. In the early 2000s, he played extensively in sessions and concerts with the Irish music groups Shelta and Bouncing Feet.

From 2007, he worked more on traditional French music, in particular the music of Auvergne. He met Michel Esbelin, with whom he created a cabrette/accordion duo. Tiennet also began to play in folk dance: this was the birth of the duo TTC (with Thomas Restoin) in 2009, then Mister Klof (with Julien Cartonnet, Sylvain Quéré and Sylvain Vuidart) in 2010.

Subsequently, Tiennet became increasingly interested in the origins of the Parisian musette. In 2014, with Solen Imbeaud and Camille Raibaud, he participated in the creation of a show for young audiences, Les Enfants du Bal, which gave birth to an album in the form of a musical tale, rewarded with a "coup de coeur" from the Charles Cros Academy. Tiennet also meets the singer Sophie Gamblin; with Antoine Leclercq on banjo, this is the start of a new musical project, Les Papillons de Nuit, which breathes new life into the musette repertoire of the interwar period in Paris.

In 2020 Tiennet founded Traucanèu with Anne-Lise Foy and Camille Raibaud, a trio which highlights the traditional dance repertoire of Auvergne, and Balam, a chromatic accordion quartet with Julien Padovani, Hervé Capel and Thomas Restoin, which offers in concert a repertoire of compositions inspired by traditional music. The same year, his first solo album was released for the collection “Un artiste, un instrument” produced by Dominique Bommel.

Alongside his activity as a musician, Tiennet gives accordion, whistle and uilleann pipes lessons. He is also asked to lead internships and master classes.