‘Two x Four’ is the snazzy title for a conceptual programme built around Bach’s Concerto for two violins and the long-standing relationship between veteran violinist Jaime Laredo and one of his most famous students (though now more of a colleague) Jennifer Koh. The concerto is the springboard for newer works for duo violinists. It’s very much a Curtis Institute of Music in-the-family occasion, with the Curtis 20/21 Ensemble accompanying faculty member Laredo and esteemed graduate Koh, both playing newly commissioned music from resident composer David Ludwig. The disc as a whole doesn’t make a compelling statement but has its charms.

Koh and Laredo duet beautifully in Bach (at the age of 73 his playing sometimes show his years, but not here). Glass’s seven-minute Echorus is minor only in its breadth: amid his typical manner, the music has a darker undertow that reminds you why this composer has been an important presence for so long. Other new pieces feel like well-accomplished assignments but not music arising from a vital impetus. Prince of Clouds finds Anna Clyne in Arvo Pärt mode, with spare, unadorned string sonorities interrupted by outbursts of fast music, though unlike Pärt there’s an extremely clever sense of musical unity between those two polarities. Ludwig riffs on Vivaldi’s Four Seasons in a variety of ways, sometimes with nervously rhythmic violin-writing that plays to Koh’s strengths. Other movements have an attractive impressionistic quality, though mainly the piece feels like a study for something bigger that’s yet to come.