I have a audio track in one MP3 file, length A-B-C-D-E in total.
I am interested to do a cut, paste and join.

What software would you recomend?

Let say I wanna cut out from point C to D and rejoint A-B-E.
How do I do it? Any software able to do that?

And the same time perhaps, I just want point C to D of the MP3 audio. How do I copy this portion out?

Hope you guys are able to help. Thanks.

To reduce file size by re-encode to a lower Bit Rate. Let say, you have a MP3 file which is in 192 Bit Rate, you may reduce it to 160 Bit Rate or 128 Bit Rate. The downside, you have less pleasurable playback. Perhaps... it is acceptable to you.