I've been encoding music for leasten on my pc at very low bitrate (like 30-40kb/s) and mono. I don't get what I want, and that's not good sound, but something that doesn't make me to cut at 12khz and fills the music with horrible artifacts. I made a set of 4 cd's with all my music, but I discovered that realaudio makes a really good job at 24kb/s. Is there something to do with mp3, or even other format at such bitrates? I think it isn't, but if anyone...
Thanks and sorry about my english...
It's quite normal, different codecs are tuned for different bitrates. RealAudio has always been targeted towards streaming, therefore it has the best tuning for very low bitrates. MP3 is not the codec to use for anything less than 128kbps.
For other codecs which might work at that bitrate you want, try WMA or MP3Pro.
I agree, VQF is very nice for low bitrates. I encoded a stereo 96 kbps piano piece and it sounded quite nice. Perhaps mono lets you half the bitrate.