Do you mean you created a drum track using the session drummer plug-in? If so, that was a MIDI track. When you mix down to MP3 in CW, it only takes the AUDIO tracks. You would need to record the MIDI drum track as a stereo AUDIO track and then mix down. OR you could mix down the audio and MIDI to an outside medium, like DAT, and then record that back into CW on a stereo audio track and mix THAT down to MP3. Then you could delete the mixed stereo track and keep the MP3. That might be a little more cumbersome, but it saves space on your hard drive by eliminating one more big stereo .WAV file. Either way will get you where you need to go. Good Luck!