Setting race without teams?

[Jaina Proudless]

Hello, in my map the race is chosen in-game as is common with altered melees. I want to set the race of all players to human to create a bug-less and deactivatable music system by simply importing tracks to overwrite the standard human ones. However I still want melee-like team selection. It sounds like it should be possible... however the races never lock for me if I do not set custom teams...