

Note: it's a double trick actually; the song in question does not originally contain a full strophe of the folk song "Prinz Eugen", but only its melody (at the end) and one line of the old lyrics. The excerpt I used originates from a wartime radio recording, where they, for a change, sung the full "Prinz Eugen, der edle Ritter" strophe, instead of just one line.
The answer's quite simple actually, one only has to pay attention to the tempo...

Cheers,
Ivan