Sonos 4 is a software real time multiband FM processor for broadcasters. With a suitable sound card it is possible to turn a Windows PC into a broadcast limiter. The processor achieves its loudness through the use of a distortion masked final clipper (a distortion cancelled clipper). The sound quality and loudness is close to industry standard Optimods and Omnias.
Sonos 4 is no longer available. It has been replaced by Radio Optimizer.
Maxx is a tool for final limiting or mastering of audio files in production environments. There is a manual interactive mode and a batch file processing mode using either a new two band (MBL2) processor or a nine band processor based on MBL9 from Sonos 4.
More information. Screenshots.
Read the getting started page if you cannot get Maxx working.