A convergence of classical, bluegrass -- almost

Just from the nature of the collaboration, it was almost inevitable that “From Bluegrass Roots: The New American Acoustic,” a Hollywood Bowl program Friday featuring the Los Angeles Philharmonic and the popular progressive bluegrass band Nickel Creek, would be rather diffuse. And by the end of the first of its two nights, only the climactic four songs truly realized the concept’s potential.

Nickel Creek is a young group out of San Diego -- fiddler Sara Watkins, her brother Sean on guitar and dazzling mandolinist Chris Thile, joined by Mark Schatz on string bass. The four showcased an imaginatively complex blend, one that reached way beyond bluegrass, owing a debt both to the ‘70s “newgrass” of David Grisman and the more recent populism of Alison Krauss.

When joined by the Philharmonic, with David Amado conducting colorful orchestrations by Sean O’Laughlin, Nickel Creek’s music took on even more dimension. The song “I Should’ve Known Better” turned sultry and sexy a la “Ode to Billie Joe,” while the twist-filled instrumental “Smoothie Song” fully integrated orchestra and band in a mini-concerto.

But the Philharmonic’s opening segment -- short pieces from 20th century icons Leonard Bernstein, Charles Ives and Aaron Copland -- was too scattershot to make any meaningful point, and only Copland’s “Hoedown” tapped bluegrass roots at all. Living composer Michael Daugherty’s rollicking “Route 66” was a treat, though, full of Bernstein-esque flour- ishes and Henry Mancini allusions.

And the opportunity to have these two ensembles team at greater length to connect the bluegrass-classical dots was missed. At the very least, Nickel Creek could have preceded “Hoedown” by playing “Bonaparte’s Retreat,” the British Isles/Appalachian fiddle tune on which it was based.