Five musicians do not an orchestra make, but the Colorado String Quartet and guitarist George Sakellariou showed the strengths of reduced numbers in chamber-sized concerto settings Saturday night at the Terrace Theater. For Vivaldi's engaging Guitar Concerto in D, only three strings (no viola) supported; Giuliani's Concerto No. 1 in A involved the full quintet. Yet in both pieces the ensemble's balance and clarity resulted in a rich sound, appropriate to the musical styles at hand. The Giuliani concerto was an especially good virtuoso showcase for Sakellariou, whose unswerving legato lines graced the final movement.

Dignity and spirit typified his playing as a soloist, whether he was interpreting a transcription of Bach's Cello Suite No. 1 or Villa-Lobos' spicy Etude No. 11. Sakellariou explored the guitar's coloristic side in Albe'niz's "Cordoba" and in "Sakura," a favorite Japanese folk song he decorated with bell-like harmonics.

The most impressive performance belonged to the Colorado String Quartet and its reading of Ginastera's String Quartet No. 2. Anguish and rhapsody dominate this five-movement work, moods the players captured with a savagery bordering on chaos. The central "presto magico" featured an expressive cadenza by each member that imitated the human voice.