Emanuel Ax's 1998 Sony release with Charles Mackerras and the Orchestra of the Age of Enlightenment of Chopin's Piano Concerto No. 2 in F minor, Op. 21, is, put simply, a delightful surprise. This performance on authentic 19th century instruments -- Ax plays an 1851 Erard piano, and the orchestra is one of the world's leading period ensembles -- is a change of pace for this powerful pianist. The smaller instrument, one supposes, brings out the unexpected gracefulness and genuinely affecting lyricism from Ax, who has been known to be less delicate and sometimes brutal on modern concert grands. But whatever drew out this gentleness, it is necessary in this fragile work, the slightest of Chopin's pair of concertos but the most nocturne-like in expression. Ax's restrained playing proves especially beneficial because it lets the extremely simple orchestration show through more clearly, and makes a better case for Chopin's choice of spare string and woodwind textures in backing a lighter-toned piano. But if the concerto proves too rarefied, much sturdier fare is provided in the Fantasia on Polish Airs in A major, Op. 13, and the Andante spianato and grande polonaise, two concertante works that have moments of serene beauty similar to those in the Piano Concerto No. 2, but are balanced with bravura passages for both the pianist and orchestra. Sony's sound quality is pleasantly balanced and naturally resonant.