This is a cas-to-wav converter. It is roughly based on cas2wav.pl, a Perl script that can be found
here and it is hosted by World of Dragon.
In order to add a 1/2-second gap after the name block (the very first block in a cas file), the whole file must be processed. Some files got their data in such a way that the processing algorithm can't read them, but the real (and some virtual) hardware can. Try to disable the gap if an error happens.
This tool was not designed for converting BASIC files. However, by popular demand this could be included as well.