NEW MUSIC WITH GUITAR. David Starobin, guitar. Bridge Records BDG 2006. This disc demonstrates the imagination that modern composers may bring to the acoustic guitar--yet reactions must be mixed. Steven Sondheim's "Sunday Song Set" is bright enough to hold the listener fast the first time, and profound enough to invite further probings. But pieces by Bayan Northcott and Milton Babbitt seem too dissonant to be attractive, and too erratic to be interesting. John Anthony Lennon, in setting music to poems by James Joyce, occasionally reveals a magic touch, but seems unable to sustain a lyrical reading of the text.