There is no end to his talent.
Here he is doing Amazing Grace on the Bagpipe:
http://www.youtube.com/watch?v=4_DqmyI_YNE
And here he is doing Dueling Banjos with daughter Ashley (Note, he already was diagnosed with Alzheimer’s then):
http://www.youtube.com/watch?v=5FY8OjT6me8
This was in one of the comments on the Amazing Grace video. How nice that he could do so many other things!
Also, I'm not surprised he could still play banjo with Alzheimers. Motor skills, especially those honed by practice, are among the last to go. My father (32 years in the Navy) could still polish his boots and iron until very recently, and he could probably still clean a gun if you handed it to him.
People also forget acquired languages. My boss's husband forgot how to speak English. He would say, "Why doesn't anyone understand English anymore?!?" and she would reply, "Manuel, you were speaking Spanish!" The husband of one of my mother's friends forgot English and could only speak German.