Question
Can one fruit tree be host to several different other fruits that have been grafted onto that tree?

Answer
Cliff,

Have been reading ads for fruit salad trees?

Grafting differing fruits onto a single stem is accomplished by using only fruits from the same genus.  So apples work, fruits from the genus Prunus (peaches, plums, apricots, etc).

Do not expect to harvest bushels of each from such a tree.  It is really only a conversation piece.

Good luck

Gary