Convert WAV file to MP3 after upload, then delete existing WAV file

I have composers who upload their music to the website. What currently happens is a WAV file gets uploaded. During the upload process, this WAV music file is mixed with another already-existing WAV file on the server, this other wav file serves as a preview version for the music and is a voice-over. The end result is that the original WAV file is uploaded as is and put in the upload-folder. The 2nd mixed WAV file is saved to another folder. So there are two WAV files, one with a voice-over and one without. What concerns me is the disk space used because of the large WAV files. I would like to have the original WAV file uploaded and kept on the server, but the 2nd MIXED file needs to be in MP3 format. This could probably be accomplished in either two of the following ways: 1. Upload the wav file, then convert to MP3 (keeping the existing wav file as well), and then mix the MP3 with an MP3 version of the voice over. If this option is chosen, there will be only 2 files. The original wav file uploaded without the voice-over and the new mixed MP3, saved to a different folder than upload. 2. Upload the wav file, do the mix with the two wav files, and then convert the mixed file to MP3. If this option is chosen, there will be 3 files, the original wav file, the mixed wav file in a different folder, and then the MP3 file after conversion. In this case the mixed wav file should be deleted so that there is only the MP3 mixed file left as well as the original wav upload without the voice-over. The programming for mixing the two wav files was done in SOX. I'm not sure if this project can be continued in SOX or if you can use another program/script together with SOX to solve this problem. Since I am on a shared server at a hosting company, I have a list of compatible scripts, software etc that is allowed on the shared server. I have a Linux shared server, so please look carefully at which options are available for SHARED as well as LINUX, not Windows. Please see this link to see compatible software/scripts/etc: [login to view URL] The column to the left shows available technologies and the middle column shows shared server info. If you have any more questions regarding this project, please don't hesitate to contact. Regards Lindy