He grew up in Trondheim and began his music studies at the Trøndelag Conservatory of Music under the guidance of. Stein Villanger. He then studied in Germany at the Freiburg Academy of Music with Ifor James (French horn) and Renée Allen (natural horns). He completed his studies at the Norwegian Academy of Music, specialising in chamber and solo music under Frøydis Ree Wekre.
. Steinar Granmo Nilsen's repertoire includes baroque and contemporary music. He performs both as a chamber musician as well as soloist, and plays modern and historical brass instruments.
He has collaborated with many of Scandinavia's leading baroque ensembles and is a regular member of the Oslo Chamber Academy. In 1999, Steinar took part in the renowned Festival d'Art Lyrique in Aix-en-Provence, France, with the L'Académie Européenne de Musique, where he performed as an orchestral musician, chamber musician and soloist - these performances earned him the title of 'instrumentalist of the year' that year. In 2000, he won second prize in the Princess Astrid Music Award.