When bears are used to people you might have to be more persistent. My harmonica playing is bad enough but some yelling and banging can help get the job done.
I was fishing in Yosemite and my wife was on the trail with a live trout in a covered pan when a bear crashed through the brush toward her. She banged on the pan and yelled but the bear just stood up, sniffed around, then slowly turned around, somewhat reluctantly. It sauntered off but turned around again for one last look. It was more like begging than threatening, almost cute.
Sleeping in the back of my campershell pickup with the tailgate down in a Mammoth campground, we were awoken at 6am with a bounce of the truck. A very large bear had its paw on the tailgate next to my head. I yelled but he wasn't fazed much. The truck lurched when it took his paw off the truck and slowly moved on, making the morning rounds.
A co-worker was accosted by an aggressive bear in a Tahoe campground while they were eating dinner at the picnic table. He said they made lots of noise but the bear didn't budge. They retreated to their popup trailer and watched the bear feast on their food. I'm sure that bear was put down.
