I've just tagged v0.10-alpha of the cores and v0.11-alpha of the Audio library.
Not much change to the cores, but they do align with Teensyduino 1.58. The Audio library has lots of fixes and features, in particular a copy of my buffered play/record objects - see https://forum.pjrc.com/threads/70963-Yet-Another-File-Player-(and-recorder).
I'm testing this but the resulting free memory is too small compared with the previous version I was using, not sure if it's because the last version of Teensyduino (because I wasusing an old version too) or the last version of the dynamic library, but the numbers are pretty different:
old version:
free for local variables:47008
free for malloc/new:194752
new version:
free for local variables:4160
free for malloc/new:6592
about the core, all I need to replace is the AudioStream.h & cpp like before?