Media Monkey freeware version:
http://www.download.com/MediaMonkey/...-10109807.html
I generally convert to WMA format 64 kps stereo for music and find the sound quality equal to MP3 128 kps stereo with half the file size. 2 MB file yields about 4 minutes of music in WMA 64 kps stereo (33 HOURS per GB). You can choose various formats and compressions to convert to when converting. I think most MP4 players will play WMA format. You may have to download and install a codec pack if you haven't already.