Audacity comes with the latest editions of knoppix. Give it a try.

If you insist on timidity: packages.debian.org
Then, as root: dpkg -i package_name.deb

I don't know what version of knoppix you are running, so, can not recommend the particular version you will need. As a matter of fact I recommend that you do not try to install it at all as your package manager suggests. If you run up against dependency issues (or a broken system), you are on your own.