To export audio files to '.gsm' format, download 'Switch' or 'GX::Transcoder' converter program for Windows. Either of these two programs is easy to use and allows audio file conversion from one format to another. All major audio file formats can be loaded and converted using these programs.

GX::Transcoder supports(MP1, MP3, MP2, MPC, OGG Vorbis, PCM up to 7.1 Channel, G.721, G.723, G.726, G.729, ADPCM, GSM, VOX, DSP, VQF and RAW files)

Switch supports (wav, mp3, ogg, gsm, dct, flac, au, aiff, vox, raw, wma, aac, atrac (.wav), ra, ram, dss, msv, dvf)

Switch download link: http://nch.com.au/components/switchsetup.exe

GX::Transcoder download link: http://www.germanixsoft.de/download/index.html

Please consult the manufacturers' sites for additional information.