$ ffmpeg -loglevel debug -y -i music_wav.wav -c:a libmp3lame -c copy -map_metadata:g -1:g -map_metadata:s:v -1:g -map_metadata:s:a -1:g -vn music.mp3

ffmpeg version N-44552-g4aade44 Copyright (c) 2000-2012 the FFmpeg developers
  built on Sep 21 2012 16:55:51 with gcc 4.4.6 (GCC) 20120305 (Red Hat 4.4.6-4)
  configuration: --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libvpx --enable-libfaac --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libxvid --enable-gpl --enable-postproc --enable-nonfree --enable-libopenjpeg
  libavutil      51. 73.101 / 51. 73.101
  libavcodec     54. 56.100 / 54. 56.100
  libavformat    54. 27.101 / 54. 27.101
  libavdevice    54.  2.100 / 54.  2.100
  libavfilter     3. 16.104 /  3. 16.104
  libswscale      2.  1.101 /  2.  1.101
  libswresample   0. 15.100 /  0. 15.100
  libpostproc    52.  0.100 / 52.  0.100
[wav @ 0x23dc240] Format wav probed with size=2048 and score=99
[wav @ 0x23dc240] File position before avformat_find_stream_info() is 4096
[wav @ 0x23dc240] parser not found for codec pcm_f32le, packets or times may be invalid.
    Last message repeated 1 times
[wav @ 0x23dc240] max_analyze_duration 5000000 reached at 5003900
[wav @ 0x23dc240] File position after avformat_find_stream_info() is 1781760
Guessed Channel Layout for  Input Stream #0.0 : stereo
Input #0, wav, from 'music_wav.wav':
  Metadata:
    encoder         : FL Studio 9
  Duration: 00:02:12.51, bitrate: 2822 kb/s
    Stream #0:0, 433, 1/44100: Audio: pcm_f32le ([3][0][0][0] / 0x0003), 44100 Hz, stereo, flt, 2822 kb/s
[mp3 @ 0x23dcbc0] Invalid audio stream. Exactly one MP3 audio stream is required.
Output #0, mp3, to 'music.mp3':
  Metadata:
    encoder         : Lavf54.27.101
    Stream #0:0, 0, 1/90000: Audio: pcm_f32le ([3][0][0][0] / 0x0003), 44100 Hz, stereo, 2822 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument
[AVIOContext @ 0x23e4940] Statistics: 1835142 bytes read, 2 seeks