First Prize winners at both the Wigmore Hall International String Quartet Competition and the Bordeaux International String Quartet Competition in the spring of 2025, Opus13 is rapidly building a reputation on the international chamber music scene. Named after Mendelssohn’s youthful and passionate A Minor Quartet, Op. 13 — the first piece they ever played together —the quartet was formed in Oslo in 2014 by four teenagers eager to dive into the world of string quartets. Now based in both Oslo and Stockholm, Opus13 comprises Norwegian violinists Sonoko Miriam Welde and Edvard Erdal, violist Albin Uusijärvi and cellist Daniel Thorell, both from Sweden.

In addition to performing standard string quartet repertoire by composers such as Mozart, Bartók, and Schubert, Opus13 are passionate ambassadors of Nordic classical and contemporary music, frequently programming works by Grieg, Stenhammar, Tarrodi, Byström, and Fagerlund. They also enjoy genre-crossing collaborations, having performed with Norwegian folk and popular music artists including Gjermund Larsen Trio, Sissel Kyrkjebø, and Sver.

The quartet has appeared at renowned festivals and series including Chamber Music Northwest (Oregon), East Neuk Festival (Scotland), International Chamber Music Festival Utrecht (Netherlands), Yeulmaru and Yonsei Chamber Music Festivals (South Korea), and Rusk Festival (Finland), as well as most of the major chamber festivals in Norway—from Bergen to Stavanger, Rosendal, Trondheim, and Risør.
Opus13 has collaborated with leading musicians such as Janine Jansen, Alisa Weilerstein, Tabea Zimmermann, Olli Mustonen, Julian Bliss, Jonathan Biss, and Anne Sofie von Otter.

Their musical development has been shaped by ongoing mentorships with Bjørg Lewis and Berit Cardas of the Vertavo Quartet, and with Tim Frederiksen in Copenhagen. Beginning in 2025, the quartet studies with Prof. Oliver Wille of the Kuss Quartett in Hannover. In 2023,  Opus13 received Norway’s prestigious Equinor Classical Music Award, joining a distinguished line of previous recipients including Leif Ove Andsnes, Lise Davidsen, and Vilde Frang.
Opus13 are the founders and artistic directors of Vinterspill på Lillehammer, an annual chamber music festival in Lillehammer, Norway.

The quartet performs on an exceptional set of instruments:
- Sonoko Miriam Welde, violin – Antonio Stradivari (1736), on loan from Anders Sveaas’ Charitable Fund
- Edvard Erdal, violin – Lorenzo Storioni (1790), on loan from Snefonn AS
- Albin Uusijärvi, viola – Christophe Landon (2008)
- Daniel Thorell, cello – Giuseppe & Antonio Gagliano (1772), on loan from the Järnåker Foundation