Sting in Northridge? Although the music business continues to be a puzzle for many in terms of how to make a living these days, that doesn’t mean it doesn’t still hold its share of intriguing surprises. Thus, one of the biggest rock stars in the annals of rock - Sting - materialized Wednesday at Cal State Northridge’s Valley Performing Arts Center, at noon no less (“Good evening!” he said after sauntering on stage, and quickly correcting himself, “Or good morning, I guess”), for a midday preview of new music before a tiny but boisterous crowd of about 300.