this is kind of overdue.
BTrack by Adam Stark is one of the few available open-source real-time audio beat trackers that is working quite decent.it is a C++ library that was unfortunately quite a hassle to compile to a 64bit version under windows (due to certain dependencies and some non-standard things like variable lengh arrays that the visual studio C++ compiler does not agree with).
nevertheless, i managed to get a version running and wrapped into a C++/CLI class that can now be used within a VVVV.Audio module.
and it works!
actually quite nicely with content that has a clear rhythm but don’t expect miracles with more difficult stuff.
i’ll clean up some more and then i’ll put it here for you to test and use.