The file format when uploading to Sonictel's Broadsoft for Music On Hold | Automated Attendants, etc. File Format
All custom Music On Hold files must be in .wav file format with CCITT u-Law or a-Law settings and 8kHz, 8 bit mono attributes.
Using a basic sound converter will allow you to save your .wav file in this format.
Maximum file size is 4.6 MB for ~10 minutes of playback.