This particular set up has Izzy Davila singing lead and playing guataca. Willie Everich is playing shekere and singing coro. Jose Rivera is playing caja and singing coro, that's it. No more singers/players! One thing Willie told me a while back which stood out is that he felt that his ability to sing and play simultaneously was the main factor that kept him working for so long. Willie told me that he felt that other players were more gifted than him but it was his ability to do the job of two men that kept him busy.
I have shared two clips below that I hope you will enjoy.