wav to mxl conversion is typically searched by users that are looking for a way to convert their WAV audio (PMC) directly into a music notation / sheet in MusicXML format, which is often saved just as .xml file or one of the compressed (.mxl) variants.
The best option is to use one of the dedicated music composition and notation software, for example MuseScore or Harmony Assistant.
Updated: October 24, 2023