The other chips, and the trades they made

A chip with filters, and a personality to match

The Commodore 64's SID has three voices but a resonant filter and real envelopes, so its music sounds nothing like the NES despite the same era.

The chip that was everywhere else

The AY-3-8910 turns up in arcade boards, home computers and handhelds, which makes it the most-heard chip almost nobody names.

A fourth channel, and headphones

The Game Boy's audio adds a wavetable channel and, crucially, was heard through headphones — which changed how people wrote for it.