In classical music, that certainly is right--the tonic/dominant modulation is just exactly that--tension and release(I am not sure how well that model explains to a lot of New Music, Schonberg and the twelve tone system, but then..)

It is interesting, isn't it, how when you play the separate intervals like that, that the chords turn out to have so much dissonance in them?

The major third interval, C-E. can sound especially dissonant, and this used to really mess me up when I first tried singing harmonies--the reason becomes clear when you look at the inversion- E-C, which is the augmented fifth interval that "Garg" mentioned earlier--

In renaissance and baroque music, the major third interval was regarded as dissonant, and they resolved to a minor third instead--(most of the melodies in folk music follow the music rules of this time period, which is why I bring it up)

If you are harmonizing in C major, and your are resolving, or ending your melody ends on a C, you could go to the A rather than the E and it will sound better--