More thoughts on recording singers...
For me, recording vocals is the most-difficult, labor-intensive recording I do. It's hard work, most of the time.
As someone mentioned in this thread, drums and guitars can get louder...but they're a helluva lot easier to record because their dynamic range is not that wide.
Think about the wide dynamics of a singer...we have to record their breaths between phrases, and yet contain a full bore chorus. The human voice is a much more powerful instrument dynamically than drums or a Marshall amp.
Generally, I try to get the amount of gain and compression I want for the loudest segment of the song, then ride the gain up (either on the pre or the output of the compressor, depending on the sound I want) during the softer portions.
Don't be fooled, recording vocals properly is hard work.
Eric Rudd