I’m recording intros and outros for podcasts.
For the last 24 hours, or you’ve been doing this since 2012 and it just started doing this?
I get a good sound and mix and export to mp3
I’d probably start by exporting to WAV and see if the same thing happens. If it does, that clears all the MP3 multiple conversion and compression tools.
I understand that mp3 is lossy,
No. MP3 problems are very simple and easy to recognize with one ear closed. This is something else.
Are you in mono the whole way? Are you trying to mix downloaded stereo music with your mono voices-over?
Do you use the little sliders to the left of your tracks to achieve volume balance and graceful presentation?
It’s a common problem that you can’t tell what the final show balance is going to be while looking at all the different tracks on the timeline. In particular, knowing when you’re going to get overload is something of a magic act.
There is Tracks > Mix and Render that I have never used. I want it to smash all my tracks into one track so I can examine it, but I think the last time I tried to use it, it doesn’t do exactly that.
It bothers me that the tonal balance of the show seems to go into the bin. That points to a non-normal problem, or a tool or process you’re using in an odd way.
Does it sound OK if you just record your voice: “Testing one, two, three” and export it? No other tracks, no other filters or effects? There are lots of ways to mess up mixing performances and existing tracks, but most of them are apparent on the timeline right away. They don’t wait to kill you later.
Do us a favor and try to hit all the questions. Too many people ignore everything but the last one.
Post a sample of voice and music on the forum. You can use MP3 so you can get quite a lot in the post. We don’t need the super high quality of WAV for this. No mater what for format, you still can’t post hours and hours.