rtmidi : RtMidi provide a common C++ API for realtime MIDI input/output across ALSA and JACK. ( http://www.music.mcgill.ca/~gary/rtmidi/ )
zita-resampler : C++ library for real-time resampling of audio signals ( http://kokkinizita.linuxaudio.org/linuxaudio/ )
Add an ebuild in portage :
The ebuild is now in the portage tree.
You can also use layman : emerge layman then layman -a dsr
For Paludis use this rsync : rsync://gentoo.zugaina.org/dsr-portage
If you have a problem : ycarus(-at-)zugaina.org