I have often noticed chord notations that call for a dissonance such as a 7 or a 9. However, in most cases, the melody (singer or instrument) is already singing the the dissonant note. In an E9 chord, if the guitar plays an E chord and the singer sings an F, you've got the E9 with no effort, because it's a team effort.

Publishers write fake books as if everyone is playing a fine grand piano in a big restaurant. Actually, we are playing flutes and whistles in a small living room. The result is that the 'interesting' dissonances they call for are too strong, too sour, and end up irritating us.

So when I see a D7 on a song, I give the D to the guitar, let a flute play the C, and everybody's happier.