The spectrum meter only tells part of the story and in many cases it tells you nothing in fact.
I am working with a female vocalist right now and we are producing 4 songs together. I recorded a scratch vocal the other day for one of the songs. On playback I could hear that although the vocal sound was very smooth and clear and nice it still had some prominence in the upper mids somewhere. Thinking I might put a spectrum meter over it and that would tell me so much as to where that might be. No so. Every time she sang the whole area from about 1K to about 6K moved up and down on the spectrum meter. It was useless at pinpointing the area I was hearing.
In the end I used my ears to identify the area of importance. I had to create an EQ curve with a sharp peak and sweep the area and sure enough I found the narrow band of frequencies pretty fast. At that point you can either emphasise that part of a vocalist's sound or attenuate it as well.
The analyser did not help a bit in that situation. It can help in other situations though. It is handy for looking at broad low and high end shapes on commercial discs for example to get an idea of how the extremes of the spectrum are shaped. I was working with a male singer once who also had some prominence in a certain area of the spectrum and the analyser did help in the situation. It showed the area quite clearly. It depends on the program material as to how useful it is to a certain extent.
Don't get bogged down in it though. Often it is useless in what it is showing you, other times it can be helpful.