Nanci Griffith brought her quest for a broad-based audience to sold-out Gaston Hall Tuesday night. Having started her career as a solo Texas folkie, she's already moved through her country phase and is now entering her pop phase. Griffith brought along six fellow musicians to match the full arrangements of her new Glyn Johns-produced album and to fill out her old songs. Far from blunting her material, these arrangements finally gave Griffith music as sophisticated as her lyrics. Her soprano is so pure and piercing that it easily sliced through the sound of the band with her image-filled stories. The rhythm section lent a needed push to her choruses, and keyboardist James Hooker (formerly of the Amazing Rhythm Aces) and guitarist David Halley (songwriter for Joe Ely and Jimmie Dale Gilmore) fulfilled the harmonic possibilities of her melodies. There's no reason Griffith can't make the transition from folkie to pop star like Judy Collins and Joni Mitchell before her. Opening the show was Texas singer-songwriter James McMurtry, who performed eight songs from his acclaimed debut album, plus another original, "The Storekeeper." The folk-rock sound of the album was tilted decidedly toward rock Tuesday night, as McMurtry led his tight quartet in confident, aggressive reworkings of the songs. Reinforcing this new assertiveness were McMurtry's vocals, which boasted a new fullness and edge. He sounded more like Guy Clark and less like Leonard Cohen, which is -- needless to say -- a huge improvement.