His early musical training in cello, piano, and percussion laid the foundation for his studies in musicology at Lund University, followed by composition at the Malmö Academy of Music (1998–2005) under Rolf Martinsson, Hans Gefors, Per Mårtensson, Kent Olofsson, and Luca Francesconi.

Staern’s compositions reflect a distinctive and deeply personal style, spanning orchestral, chamber, solo, electroacoustic, choral, and operatic works. A defining aspect of his creativity is his synesthetic ability to associate tones and timbres with colors, influencing works like Yellow Skies, Colour Wandering, and Air–Spiral–Light.

From 2010 to 2014, Staern was composer-in-residence with the New European Ensemble, leading to major works such as Tranströmersånger (based on poems by Tomas Tranströmer) and Bells and Waves, which won the SMFF Award in 2011. His multimedia work SAIYAH, created with Yoko Seyama, premiered at Norrlandsoperan during the MADE Festival in 2014. His Clarinet Concerto – Worried Souls earned the Large Christ Johnson Prize in 2012 from the Royal Swedish Academy of Music.

In 2016, Staern was recognized as “Composer in Profile” at the Båstad Chamber Music Festival before premiering his first opera, Snow Queen (libretto: Anelia Kadieva Jonsson), at Malmö Opera to critical acclaim. His second opera, HILMA: An Opera About Hidden Art (libretto: Mira Bartov), explored the life of Hilma af Klint and was performed at Stockholm’s Moderna Museet and New York’s Guggenheim Museum.

A composer weekend at Stockholm’s Konserthuset showcased thirteen of his major works, including two world premieres. He is currently “Artist-in-Residence” with Västerås Sinfonietta (2023–2026). Staern also contributes to music education, lecturing at Falun Musikkonservatorium, Båstad Chamber Music Festival, De Geer Gymnasium in Norrköping, and the Gotland School of Composition.