Question

what is the inheritance pattern for many phenotypes produced by more than one pair of alleles

Answer 1

It sounds to me like "polygenic inheritance."

"Polygenic inheritance" is where a trait is determined by more than one gene.

For example, our hair color is determined by more than one gene.

That's why there are so many different hair colors,
with so many "in betweens," like dark brown, light brown, strawberry blonde, and bright blonde.

There are lots of different possibilities for hair color.
And that's because hair color is determined through "polygenic inheritance."