how to have inconsitent vocals at the same volume?

Hello My vocalist recorded my new song in two sessions on MC5 through a Samson Q7 mic. Now i realise the volumes of the individual sections are not consistent accross the song. Is there a way i can get the singers voice at much the same level throughout the song without altering each segment manually? Thanks Jason (these links are not to the new song.. it's not out yet) http://soundcloud.com/jason-king-16 http://youtu.be/yw8Z3OuIeig

In other words...The way I see it, adjusting envelopes IS very much manual labor, segment by segment, but that's what you need to do.
After that you can add some compression. Trying to squeeze it only with a compressor, without the volume envelopes, would most likely give less satisfactory results.

Normalizing does not sound like a very good idea for this type of jobs, but if the segments themselves are of consistant and nice level, but just different from each other, then normalizing will help. At least to get you to an easy starting point. It needs to be done segment by segment, otherwise the relative differences remain. Note, that if there are parts that are meant to be soft and quiet, then normalizing will raise those as loud as the loudest parts.
And one single loud shout close to 0 dB forms a spike that prevents the normalizing to raise the overall level, so such spikes must be edited by hand/envelopes beforehand. IF you use normalize, don't go up to 0 dB, -2 - -3 dB is better,
or, if you're about to add FX, even lower.

envelopes work well..... the best way however is to get it as close to right going in. 

Since there were 2 sessions, the thing to have done, to do it right would be to record a short snippit in session 2 and listen to be sure tone and volume were as close to the original as possible. 

You don't just want to turn it on  and go..... even in a time crunched demo session..... you want to take the time to get things set up correctly.

Talk about taking your time to go segment by segment......when I work on the pitch correction of a vocal track, I literally go note by note through the entire vocal track examining and listening to each note and then sometimes working on one note for several minutes..... 

I guess it comes down to the question of just how much time do you want to spend on something to get it right?