If you were hearing Mozart’s K449 and Beethoven’s Fourth Concerto for the first time via these reductions for string quintet or sextet and piano, you wouldn’t suspect that anything’s amiss. This is partly due to the intense and enlivening contributions of the Borromeo Quartet (and colleagues), matched note by note and point by point by David Deveau’s mindful, stylish virtuosity.

The ensemble sustain the Beethoven first-movement ritornello’s broad basic tempo with a degree of note-to-note inflection that more than compensates for the particular tonal qualities of Beethoven’s instrumentation (the second subject’s plaintive solo oboe, for example). The finale’s rapid exchanges between piano and strings not only benefit from the elevated chamber interplay resulting from reduced forces but also allow for subtle tempo fluctuations, and for the scurrying bass lines to emerge with refreshing clarity. Listeners will notice how the strings’ fierce projection and focus of the slow movement’s declarative unison tuttis provide a foil to Deveau’s plaintive reserve.

Nor are the Mozart readings any less intelligently detailed. In the finale, the easy-going repartee between piano and strings yields bracing contrapuntal cogency, while the slow movement’s operatic melody lines and relatively modest accompanimental figurations emerge with shapely and meaningful interaction. Composer John Harbison’s cadenzas for the Mozart are thoroughly idiomatic but not so imaginatively wrought as his Beethoven cadenzas, which admittedly venture on occasion into early Brahms/Fauré harmonic territory. Late Fauré, however, appears to be the jumping-off point for Harbison’s gorgeous little Anniversary Waltz, an impression enhanced by Deveau’s sensitive performance. I also like his ripe and vocally informed Mozart K396 Fantasia, featuring bass lines that resonate and soar to the heavens. Excellent sound and annotations add to this disc’s appeal.