Haw! I saw Captain & Tennille in a little bar once upon a time. Not really by choice-I was working there and the outdoor show got moved inside. '73, I think. I musta been about 15. Darrell "The Captain" Dragoon (sp?) just passed a couple months back.
I've tried to post them links like you told other Larry to, but it don't seem to work for me.
At any rate, as for evolution, consider Crossroad Blues
Robert Johnson:
http://youtu.be/Yd60nI4sa9A
Cream:
http://youtu.be/aVH_si6N5pM
Skynyrd:
http://youtu.be/Z6wpoeL-Tbs
Adam Gussow (with a fine truck. IDK if it's his, but it's a nice one)
https://youtu.be/KeMis-B7f58