I would like to play a character who excels in impersonating people. Of course, a high Deception skill comes in handy. But what if I want to impersonate an elf, a dragonborn or an orc? (Alter Self, a Disguise Kit or other such tricks are viable options). People would probably expect me to speak Elvish, Draconic or Orcish. And that's my problem. I can grab some languages with the changeling race, and some more with an appropriate background. I think a Knowledge Cleric would also get some extra languages. But still, my character can never know EVERY language.
That’s where the Tongues spell comes into play. In older editions this spell would let you speak any language. But I’m not sure about the 5th edition version of Tongues. It only says …
This spell grants the creature you touch the ability to understand any spoken language it hears. Moreover, when the target speaks, any creature that knows at least one language can hear the target and understands what it says.
Can I fool listeners with this spell? Would an elf actually believe that I talk to them in Elvish? Or would any listener recognize that I only make myself comprehensible with magic?