Forget the Yo-yo (boring.......boring.....boring..... although an interesting trick with a toy when I was younger) and go directly to Fournier (best of the lot or the other great French 'cellists who also got it right (Tortelier, Navarra and Gendron). Casal's is interesting as well as the first (mid-to-late 1930's) as is Starker who has recorded the cycle at least four times. To move up in time.....Kodaly, Hindemith, Colgrass, Sessions, Britten and Henze are interesting places to visit. I say this from having performed all of the pieces cited frequently. Peter Schenkman, Toronto, Canada