The k3b build includes options for the musepack decoder and musicbrainz.
The old versions required are:

Musepack
""""""""
The libmpcdec source for the musepack decoder
https://files.musepack.net/source/libmpcdec-1.2.6.tar.bz2

Musicbrainz
"""""""""""
The libmusicbrainz-2.1.5 source
http://ftp.musicbrainz.org/pub/musicbrainz/historical/libmusicbrainz-2.1.5.tar.gz

If these are placed in the 'src' directory, the packages will be built and installed during the k3b build.