The featured enhancement for this release is the addition of multithreaded operation to the WavPack library code (libwavpack). This can significantly speed up decoding and encoding operations, sometimes as much as 6X or more (assuming a multi-core CPU). An option was added to the command-line programs to utilize this (--threads) and the Cool Edit / Audition plugin was updated also. Clients of the library can easily enable this as well, but it is not the default behavior (see the last section of the library documentation for details). Under the hood this feature uses pthreads on POSIX compatible platforms and native threads on Windows.
The ability to import ID3 tags has been enhanced with more item and picture types, multiple values per item, and now ID3v2.4 tags are handled including all their text encodings. A bug that caused trouble seeking in very large files was fixed on Windows, and a new mode (--optimize-int32) was created for 32-bit integer audio originally sourced from float that improves compression by 10%.
Because the measured performance of the command-line programs on Windows was consistently better using MinGW builds, I have switched from MSVC to that for the official binaries.
For the remaining minor fixes and improvements, see the official NEWS file.
Note that I am no longer able to generate binaries for macOS. These should probably be obtained from HomeBrew anyway, and they have already been updated 5.7.0.