THANKS for your interest.
1. In Sound Editor I click on Add Audio File and select my music (4 min 30 sec).
2. In the Mix Editor, I click on the "Plus" icon in the Layer 1 box which presents Layer 2
3. I press the Play button at the bottom of the screen and play the music to the spot (1:17:47) where I wish to mix in 1:06 in Layer 2.
4.I highligtt Layer 2, then click on Add Audio FIle, double-click on the audio to be mixed in.
5. I back up the time line to just before where the Layer 2 clip should mix in, press the Play icon at the bottom of the screen and insure the Layer 2 clip is in the correct place (If not, I right-click on the Layer 2 clip, select Zoom to Clip and manually adjust it, then right-click on the clip again and select Zoom to Full and repeat this step as many times as necessary to get the clip in the correct spot.)
6. I repeat Step 5 EIGHT total times (I have EIGHT Layer 2 mixes added to the original music in Layer 1).
7. Today, unlike yesterday, when I press Export Mix - it worked!!!
When I play the mix, the Layer 2 clips play progressivley later in the mix (when I was added them originally, I was very careful to play the mix back and all eight Layer 2 clips played the the correct place) and prgressively more garbled (again, when I played the original mix before exporting, it played flawlessly).
I know the problem has changed from yesterday, but there is still a problem with the completed mix.
Any help would be very appreciated.