A couple of the tracks that I am burning are digital recordings of lectures.  They average about 40 minutes each (2X40= 80 minutes) and I can only get one lecture per CD.  I waste 30+ minutes of usable space on each CD.  The CDs are cheap, it is the annoyance factor that I am trying to avoid (ie. Switching CDs to get to the second part of a lecture while travelling at 70 MPH)

I keep wasting space at the end of the CDs.  The label of the CD-R claims it will hold 74 minutes of audio.

Since a few of the tracks that I want to remix cause me to go to a total time of 80+ minutes, is there a way to reduce the audio quality in order to get more use out of the CDs and still have it encoded so that my car can recognize it as audio?  My Sony car stereo will read a CD-R,  CD-RW but it will not read a native MP3 (ie.  encoded as data, not audio data)

I am using 'Ahead Nero' to burn the CDs and the media is HP CD-R 650MB/74min

Why dont you use the 80 min media?  My (way) old Sony head unit reads and plays 80 min disks...  

Because, I don't have 80 minute media here.  I have some FREE 74 minute media.  Besides, some of the lectures are 45 minutes and that takes me past the 80 minute mark as well.

What I want to find out is how to reduce the quality of the soundtrack to reduce its complexity, quality and size.

You can't reduce the bitrate, you have to speed up the recording. You can probably do this using WinAmp, with the right plug-ins.

Another idea would be to combine both parts into one file, the first part in the left track, the second part in the right, and use you L-R fader to listen to each part separately.

Changing the sample rate and all can be done to reduce the size of the files...BUT...you're burning them down to a standard CD which records in whatever that format is so you're stuck with dealing with the material in a 'time' sense as in how much time is the material, not how big the files are because the burning software will simply convert the data over.

Now if you had a CD player that read MP3s you'd be set.

Jetlag's idea of putting part one on the left part two on the right is the closest you're going to get with a one CD burn of this material.  To do that, you'll have to open both MP3s into a wave editor and do some copy/pasting.

Ok, that clears it up.

I had hoped that the 'time' issue was based upon file size/sample rate.

I like the idea of using left and right tracks to tune in/out each half of the lecture.  I will experiment with this and see what the results are.

Rats.

I guarantee you the next time I buy a Car audio system it will be capable of playing native MP3's, don't let phrase "Plays CD-R, CD-RW" convince you that it plays MP3's.  My mistake, that is for sure.

If he doesn't talk too fast already you might want to consider time-compressing the files. You can download a demo of [url=http://www.syntrillium.com/]Cool Edit 2000[/url] and do it. I could give you a quick tutorial on how to do it (not many steps at all).