Emanuel Ax HAYDN: PIANO SONATAS NOS. 29, 31, 34, 35 & 49 (SONY CLASSICAL)

Haydn’s 60-odd piano sonatas are among the least-known works in his output. As a total body of work, they seem to lack the groundbreaking spirit of the symphonies and string quartets, genres that Haydn can fairly be said to have invented. Even so, they’re delightful works that have more than their fair share of experimentation. Haydn’s gift for invention was second to none, and the sonatas are full of unexpected melodic and harmonic twists and turns that show both musical sophistication and an earthy sense of humor. Hearing this disc multiple times, you’re still apt to be surprised by the sudden changes in register, dynamics, and key — qualities that set Haydn’s sonatas apart from most of Mozart’s. They don’t carry the kind of emotional weight with which Beethoven would infuse the genre, but Haydn’s ingenuity certainly set the stage for Beethoven’s monumental forward leaps.

It is difficult to imagine these works being brought off any better than Emanuel Ax does here, on his third Haydn go-round. He brings ebullience, a solid understanding of Haydn’s style, and all of the modern piano’s timbral resources to these recordings. His playing has solidity and weight — check out the imposing opening to No. 49, the only minor-key work here — but the rondo finales are tossed off with sparkle and grace, especially those of Nos. 31 and 35. Lines sing, and Ax’s ornamentation and use of rubato can only be described as tasteful, an adjective by which Haydn set the greatest store. This is a wonderful introduction to some unjustly neglected works.

(Emanuel Ax will play Brahms’s Piano Concerto No. 1 with Christoph von Dohnányi and the BSO, on a program with Dvorák’s Symphony No. 9 (From the New World), at Tanglewood on Sunday August 3 at 2:30 p.m.; call 888-266-1200.)