TwoLAME is an optimized MPEG Audio Layer 2 (MP2) encoder. TwoLAME should be able to be used as a drop-in replacement for LAME (a MPEG Layer 3 encoder). The frontend takes very similar command line options to LAME, and the backend library has a very similar API to LAME. You'll need to have libsndfile (also available from SlackBuilds.org) installed if you want to build the twolame frontend (which you'll almost certainly want). :)