Philip Glass invented yet another new musical phenomenon the other night: the pop/classical song-cycle summit meeting. The grand finale of his latest concert here crowded the stage with Glass's own ensemble, a baker's dozen guest instrumentalists, and an improbable lineup of singers: rock star Linda Ronstadt, operatic tenor Paul Sperry, jazz vocalist Bernard Fowler, pop crooner Janice Pendarvis, and the Roches.
Performing the last portion of Glass's popular ``Songs From Liquid Days,'' most of the singers belted out a rhythmic riff while Ronstadt soared through an obbligato that could have graced a '50s rock hit by the Diamonds or the Five Satins.
The vocalizing was heavily amplified and supported by plenty of woodwind and keyboard instruments (mainstays of the pop and jazz scenes) in addition to strings and brass. It was an exciting combination of elements and one that's impossible to label - a living metaphor for the ``crossover'' popularity that attracts both rock-lovers and classicists to Glass performances.
Although the bestselling ``Songs From Liquid Days'' album (CBS FM 39564) is being sold as a classical disc, its live-concert premi`ere at Lincoln Center had the electricity - plus the decibel level and some of the personnel - of a rock spectacular.
The event (which was repeated in Los Angeles and San Francisco over the next few evenings) thus raised a key question: Is composer Glass veering more toward mass-market popularity of the type he sought with his uneven ``Glassworks'' record, than toward the uncompromising orchestral textures of his latest operas, ``Satyagraha'' and ``Akhenaton''?
There's no reason why Glass can't bring both the Juilliard School and the disco-hopping sides of his personality into his compositions.
Other pieces performed at the Avery Fisher Hall concert showed him still capable of doing this - one being a thumping score based on ``A Descent Into the Maelstrom,'' by Edgar Allan Poe, the other a swirling dance (strongly recalling his exquisite Dance No. 1 of several years ago) written for ``In the Upper Room,'' a new work choreographed by Twyla Tharp.
``Songs From Liquid Days'' lacks the rigor of these pieces and seems uncomfortably eager to please, even more in live performance than in its recorded version.
Still, it compensates with some engaging lyrics (by Paul Simon and Laurie Anderson, among others) and a more original treatment of ``minimalist'' techniques than some other Glass works have shown lately.
Its pop inflections may be turning off classicists even more decisively than a past outing like ``The Photographer'' did.
It remains to be seen if they're also shaking the core of serious Glass listeners who value his past avoidance of easy pop mannerisms as well as his radical new approach to the classical vocabulary.