The "traditional" myth
By "traditional milonga" many people mean a dance where only golden age tango/vals/milonga is played.
This is a modern invention.
Consider Alberto Podesta's description of milongas during Tango's Golden Age: 1,000 people, low admission, only live bands, and "50/50 music" -- 50% "tango/vals/milonga" and 50% "whatever else is popular" -- with 40 minute alternating sets.
This is where our traditional tango recordings come from. Draw your own conclusions about what milongas of the present or future should be like:
http://youtu.be/VV5uloZgZrE?t=6m22s