@jlelse how do you add just audio? Web? Cos on iOS only option for files is from Photos (I am M.b Premium)
@warner You can do it on the web. There's also an iOS app for M.b called Wavelength that's you may want to try.
@warner If you already have an MP3 file, another option is to upload it from the Uploads screen on iOS, then copy a link into a new post. Wavelength on iOS will let you record and edit too, though.