RALEIGH, N.C. — Hiroshi Arakawa strummed his guitar, lips pursed thoughtfully. “I don’t know if I can play it now,” he admitted. But he gamely started in on “Bill Cheatum,” a bluegrass instrumental he used to blaze through with ease. This version was more tentative, with a flub or two. Arakawa grimaced at each one. “I’ve…