Audio selection

How does audio work with DVDs when you burn them? If you choose both 2.0 and 5.1, how does the DVD player know which one to use being most burned DVDs do not include the menu? My DVD player is really old and I do not have the remote. Do modern DVD players let you change which audio you are listening to? Are the audios labeled so you know which one you are switching to? Can you do this on the fly during the DVD?

THANKS.

Video-DVDs have to be authorized, and that info about streams are included into IFO and BUP files on a VideoDVD.