You miss my point entirely Magne.....Self expression means freedom to express in any way you want either by ignoring or using any rules you see fit. The minute rules HAVE to be adhered to this applies constraints and that restricts expression.
There are some occasions where we need rules and some rules are worth adopting. But not all the time.
The biz by nature will only bet on a sure fire winner. They seldom take a chance with rulebreakers and now more than ever in popmusic they want complete control. They make the rules and that IMO stifles and stagnates music.
The John Lennon winners do a good job...but that seems irrelevant to any argument about expression and constraints. I can of course make a huge long list of one dimensional music where people had the formal constraints of writing to a prescription formula where rules have to be adhered to.
As I said earlier people with narrow minds will find, if they are lucky, one way of doing something. Whereas broad minded people will develop many ways of doing things and find many different things to do.
Some people like working to a formula whilst others like experimenting and trying out new ideas. I have nothing much against those who work to a rulebook.....I sometimes do it myself.

http://www.soundclick.com/bands/songInfo.cfm?bandID=687727&songID=5238055