"Passing By: Songs by Jake Heggie": Isabel Bayrakdarian, Zheng Cao, Frederica von Stade, Susan Graham, Paul Groves, Keith Phares, and Joyce DiDonato (Avie)

What on Earth is going on here?

That question pops up early on in this disc of songs by opera composer Jake Heggie in a series of duets for two female voices, one being a wacky tango characterizing a woman arguing with her dead mother -- with mom arguing back. Susan Graham and Frederica von Stade have a grand time with the words and sound great together on a disc that inevitably challenges any conventional ideas about what constitutes a song. Although Heggie's conservative idiom isn't going to rock anybody's boat, he's game for a wide range of texts, including the final monologue from Terrence McNally's play "Master Class."

Elsewhere, Heggie's attractive "Here and Gone" cycle is written for tenor, baritone and piano quartet, happily recalling Vaughan Williams' "On Wenlock's Edge." The singing is as fine as this distinguished lineup promises to be, although the composer is so respectful of them at the piano that the songs could make an even better impression with a more challenging presence at the keyboard.

DAVID PATRICK STEARNS, PHILADELPHIA INQUIRER

Arvo Pärt: Symphony No. 4; Los Angeles Philharmonic, conducted by Esa-Pekka Salonen (ECM)

About 38 years separate Pärt's third and fourth symphonies. Between them is a succession of sacred, so-called "holy minimalist" choral works on which this much-beloved composer's reputation rests. A first listen to this new piece, however, might leave you wondering if that's such a big deal: The symphony sounds like Eastern European rainy-day music. Closer inspection reveals a network of mysteries: Although inspired by the idea of guardian angels, the symphony contains nothing conventionally beatific; its lack of typical long-term logic is extraworldly, however.

In effect, the piece is a cortege of recurring sounds -- a flourish of string pizzicato, a splash of finger cymbals, a gravely intoned harp note -- all seeming to have an emotional relationship with one another, but not an obvious one. The performance by the Los Angeles Philharmonic is tentative but not fatally so.

Filling out the disc are excerpts from the previously released "Kanon Pokajanen," which shows Pärt on familiar sacred-music ground in an Estonian Philharmonic Chamber Choir performance that knows exactly what it's about.

DAVID PATRICK STEARNS, PHILADELPHIA INQUIRER