Fixing gaps caused by the time shift tool

I am using Audacity 2.3.2.
Is it possible to fix gaps in an audio track caused when the time shift tool is used to synchronize music?
I have recorded two pieces of music and want to get them synchronized as close as possible. I have used CTRL I to create a break and the time shift tool to correct timing. Sometimes this results in a blank gaps in the corrected track.
What is the best way to avoid these gaps? Is there some function that can fill in the blanks?
Thank you for the comments.

What sound do you want to fill the blanks with?

I would like the blank spots to be filled with something that sounds like surrounding music, if that makes any sense at all. What I am trying to do is correct the timing of a piece of music. It would be far easier to play the music at the correct tempo but even then there are areas where the beats do not match up. Small shifts are not much of a problem but larger errors are harder to hide.
Thanks for the response.

Thanks, that’s what I guessed.

Got it.

Splitting and shifting is not the right approach because, as you have discovered, it leaves gaps.
If I understand correctly, you want one track, or part of a track to be longer (slower).
The tool to use is the “Change Tempo” effect. The option “Use high quality…” needs to be enabled for this job.

Thank you. I will give that a try.