Well as a example i will use one of the greatest prog epics of all time: Close to the edge...
One of my favorite aspects of this is that after 8 or 9 minutes it goes from this loud and funky opening to a more Dreamlike and quiet section where the phrase: I get up i get down is repeated several times. This section i think serves two purposes, the first being a contrast to the loud and frentic opening and the second is serving you a bit of a boring spot in the music.
Now this section is not ugly sounding but it lacks a strong melody and i dont think this is many's favorite spot of the song...infact i think about 1 minute into it you are all expecting Rick Wakemans fantastic Keyboard solo and Squires incredible Bass riff again...and i think that is just the purpose of this section, it is supposed to awake anticipation and excitement and when Wakemans Keyboard hits for a brief time it kind of teases you before it goes back to the I get up i get down section until it finally slips into the highlight: (atleast for me) Wakemans keyboard solo.
And i really think that this bit of boring section actually enhances the effect of that solo and makes the song much better than if the Keyboard solo just would slip in right away after the frentic opening...
Therebefore i think that sections that sound a bit weaker than rest of the song can make a good song even greater than if it just was a couple of semi-good riffs instead. Infact i find many songs that opens up with a tremendous intro is a bit boring as the best part of the intro is the cool riff while the rest of the riffs are just semi-good...So a better opening would be to open with a good riff and then a weak part and then the really fantastic riff to keep the listener going all the way...
I think there is a lot of this trickery In the mars volta's songs and although i dont think it is meant on purpose it surely makes the songs sound alot greater in my opinion...im sure you wont agree with this at all ![](smileys/smiley9.gif)
And i dont think that only good music is made this way but i think alot of the great prog epics uses this trick and i really like it... ![](smileys/smiley9.gif)