Reduced Train Fares - Vienna-Salzburg-Munich

There are a lot of different ways you can do this, depending on what you want to commit to (i.e. the time in Salzburg and the cost.) German Rail offers an advance purchase fare from Munich to Vienna for as low as €29/P. These fares would include travel on the fast RailJets if that's what you book. The fare is train specific, but if you want to spend a predetermined time in Salzburg, you can use the "stopover" function on the German Rail website to specify it, and the two specific trains into and out of Salzburg will allow you that time. On the other hand, if you are not so concerned with speed of travel, you could have complete flexibility with a €29 Bayern-Ticket from Munich to Salzburg and a €28 Einfach Raus ticket using regional train from Salzburg to Vienna.

Ops. I misread your itinerary. You're going from Vienna to Munich not from Munich to Vienna. Although you can build in a stopover in Salzburg going from Munich to Vienna with a Europa-Spezial ticket, you can't do it the other direction. But you can get an advance purchase Austrian Rail Sparscheine ticket from Vienna to Salzburg starting at €19/P, then go from Salzburg to Munich with a Bayern-Ticket for €29 (for 2P). The Austrian Rail website is at www.oebb.at. I'd use the Bayern-Ticket from Salzburg to Munich, because it give you complete flexibility as to the time you can spend in Salzburg and costs less than a Savings fare ticket. Salzburg to Munich is only about ½ hr longer by regional train with a Bayern-Ticket vs an express train with a Saving fare. You could also get the German Rail Europa-Spezial fare from Vienna to Munich and just get off in Salzburg and continue later with a Bayern-Ticket, but it looks like that would be a more expensive option.