Recordings

After I record a part of a meeting I wait for the pop up to tell  me that it is ready ,  then i go into the recording area of the site,  I delete the video file,  and the translation file  leaving only the audio file.    I then download it to my computer.   It downloads as an MP4 file,  which is not how I want the file to download.   How can i get it to d/l as mp3? 

also,   Out of the 3 files that are recorded when using the recording feature.   I always delete the video and the translation.  (first and last file listed in drop down list)     Is it possible to turn off the creation of the video recording and the transcript prior to recording?   That way only the audio is created?