The vowel sound is different between past tense and present tense "read", even though they're spelled the same.

But that's not what's going on in the Swedish example above. The vowels are exactly the same between "anden" (the spirit) and "anden" (the duck), but the pitch accent is different, the "song" of the words is different.

Here's a video showing the difference:

https://www.youtube.com/watch?v=lXp7_Sjgm34

(And if you can't hear the difference in that video, don't worry too much, it's Swedish that's weird, not you. :) )