Nch Software Soundtap [win-osx] -

Can be used to convert proprietary or "uncommon" audio formats into standard MP3s by playing them through a compatible player while SoundTap is active.

by NCH Software is a specialized utility designed to capture any audio playing through a computer's speakers. By using a virtual kernel driver, it records audio in high-definition digital quality, making it a popular choice for archiving webcasts, recording VoIP calls, and converting uncommon audio formats. Core Functionality NCH Software SoundTap [WiN-OSX]

Widely used by businesses and podcasters for recording interviews and conference calls. Can be used to convert proprietary or "uncommon"