The following post is by Dr. John Rachow. John serves on the national board of Physicians for Social Responsibility (hence his use of Rondee for conference calling) and recently investigated options for converting Rondee audio files.
“I tried The FreeAudioConverter at the brothersoft site. Despite the description of the program it does not seem to support .gsm. Further during installation, I am told that the product will not work full featured unless I install their (purportedly free) security suite software, System Guard. It got more complicated and invasive after that. I unloaded it all.
I had tried FXBear Audio File Converter (I had purchased it earlier in the week). It does not successfully convert gsm files as it claims to do. Since I purchased the software ($38) I have queried their support people. The FXBear interface is certainly simple and it did look like a good solution.
Last night I searched further and found NCH Swift Sounds (Australian based company http://www.nchsoftware.com) and installed their free Switcher audio file converter. With this product, I stopped looking. The link is:
Installation is super fast and simple It is a compact program (553 KB) with a sophisticated looking but easy to use interface. It works fine, converting the Rondee .gsm file to other formats quickly, including .mp3
They also have a free audio file editor, WavePad. that that allows editing a wide variety of native audio file formats including .gsm. WavePad allows you to save the file in any of a wide variety of formats (allowing you to set all the sampling and bandwidth parameters unique to each format in the process). Editing options include applying a variety of effects (noise reduction, equalizer, volume, band pass, echo, flange, and others) In effect, Wave Pad also can be used as a file converter as well as an editor. Switcher only does one thing, convert formats and has a more very simple interface.
NCH has versions for both Window and Mac. They have a Linux version for WavePad and the Linux version for Switcher is coming.”