ROCKPORT — The Vermeer Quartet will be joined by guest artists in a performance of Mendelssohn’s String Octet at 8:15 p.m. Thursday and Friday, July 15 and 16, at the Rockport Opera House.

Joining the Vermeer Quartet will be violinists Ronald Copes and Michelle Markarski, violist Bernard Zaslav (a former member of the Vermeer Quartet) and cellist Ko Iwasaki. Copes, Zaslav and Iwasaki are members of the faculty at Kneisel Hall in Blue Hill.

In addition to performing the Mendelssohn Octet, a piece written when he was only 16 years old and considered one of the masterpieces of chamber music literature, the Vermeer Quartet will play Haydn’s string quartet Op. 64, No. 1, and a more contemporary quartet by Ligeti.

Tickets are available at Heather Harland in Camden, and Reading Corner, Rockland. After 6:30 p.m. on the nights of the concert, tickets will be available at the box office.