Why can't & and ; be used together (two processes started, first in the background)?

I tried this simple test ping [SOME IP] &;ls expecting the output of ping to overlap with the listing. Instead, I got an error: > bash: syntax error near unexpected token `;' It does not help adding spaces. If the semicolon is escaped, the first command starts, then error > ;: command not found It almost works to enclose the ping in brackets (ping [SOME IP] &);ls The ls runs to completion, then the ping starts. I could achieve that more easily by typing ls;ping ... Is it possible to start two processes together, when the first (or both) are in the background?