New Zealander Hayley Westenra has the sort of soprano voice that defies qualitative judgment.

British critic Ian Sime was on the right track when he compared it to "camomile tea and essential oils [that] aid sleep and recovery" -- how can one make a judgment about those (although he does warn the listener not to listen to Westenra's new album, Treasure, "while driving at night or working with heavy machinery")? Westenra's soprano is silvery, pure, not especially expressive but with an attractive way of getting gentler as it rises.

This, her third album (she was 19 at its release), may be a good place to start for those unfamiliar with the singer.

She mixes Western classical songs and simple operatic selections with traditional tunes, some of them drawn from New Zealand's Maori heritage, and she has a way of sounding the same through all these types, which may lead to the conclusion that you'll either like her or hate her.

On Treasure, however, Westenra broadens the range of music she tackles in an interesting way -- and it would seem, since she composed or co-composed several numbers herself, that she can be credited at least with input as to the rest.

Sure, there are "Danny Boy," "Abide with Me," and "Shenandoah" here, but there's also American folk/country songwriter Cheryl Wheeler's "Summer Fly," a genuinely complex tune that Wheeler might never have quite imagined being sung this way.

Westenra doesn't quite have the maturity to pull this ambitious song off, but she achieves an attractive quality in her middle register that evokes the voice of Irish singer Mary Black (although the likely source is Maura O'Connell's recording).

It may be a bid for pop stardom, but it enlivens the program.

"Melancholy Interlude," Westenra's own sort of fantasy on ideas by John Dowland, also represents a broadening of her range.

Westenra's innocent, rather monochrome singing hasn't changed, which will be good news for her hardcore fans (Charlotte Church never quite had fans like hers, and Westenra is a more distinctive talent than Church ever was).

But what has changed is the depth of the background.

Another thing that can be said in Westenra's favor is that fitting her voice to electronic rhythm tracks would have been very easy to do, but she has largely resisted the technique.

The contributions of synthesizer programming to Treasure are sparse and subtle, and in this case that works in the music's favor.

The result is an album that will please Westenra fans and also likely broaden her reach in the crossover sphere, perhaps extending it to the less friendly United States.

Note that this album overlaps considerably with Westenra's Celtic Treasure release, which rearranges the tracks, omits a few (like the Maori "E Pari Ra"), and adds a few more.

This more varied program is preferable.