I have used "aactomp3 1" in my prefs file for years to obtain 120k mp3's. I see with the latest update, I'm getting 320k. What do I need to do to obtain 120k now please? (All of my programmes are radio and speech, and go into iTunes).

https://github.com/get-iplayer/get_iplayer/wiki/modes

--radiomode=better

The questions though are:
(a) why transcode to MP3? iTunes plays M4A (AAC) just fine
(b) why not use 320kbps? Is it because of the filesize? For speech I get that 320kbps is overkill, but for music the frequency spectrum is greater on the 320kbps files and so the audio quality is better.