The best thing about making plans is that you always get to make a new one. So when you schedule a performance by a trio, and two-thirds of the musicians can't make it, move to Plan B.

And Plan B looks pretty good when it stars a winning violinist on her national victory lap.

The changes at Musical Masterworks this weekend seem like anything but second best. Taking the place of indisposed violinist Stefan Jackiw will be Tessa Lark, a 23-year-old who just won the 2012 Naumburg International Violin Competition, one of the nation's top instrumental awards. Lark's presence will also change the program for the concerts Saturday and Sunday. Move over Stravinsky and make room for Bach. Lark will open the concerts with a show-stopper, one of the most profound of all Bach compositions, his Chaconne in D Minor for solo violin.

She will then be joined by Masterworks artistic director and resident cellist Edward Arron and pianist Jeewon Park, who is sitting in for Jeremy Denk, the other missing two-thirds of Plan A. Arron's wife and a Masterworks regular, Park's pianistic talent is well-known to audiences in Old Lyme.

The program also includes Estonian composer Arvo Pärt's new spin on the old, his 1992 Mozart-Adagio for Piano Trio; Haydn's old spin that sounds new, his Piano Trio in A-flat Major, Hob. XV:14; and Schubert's beloved Piano Trio in E-flat Major, D.929 - strangely enough, in its first Masterworks performance.

The Bach and the Schubert are two of the pillars that support this whole concept of chamber music. Plan B looks like an A.

- MILTON MOORE

Musical Masterworks, 5 p.m. Saturday and 3 p.m. Sunday, First Congregational Church, 2 Ferry Road, Old Lyme; $35, $5 tickets for students; 860-434-2252 or www.musicalmasterworks.org.