Sometimes customers recorder apps record in m4a or mov video file formats, not an mp3. For the Bluetooth Controller to play the file it must be in an mp3 format. So video files like m4a and mov need to be converted to mp3 before copying the file to the sound module.There are several free tools online available to do the conversion. We've had customers for years use CloudConvert successfully to convert most file types to other file types. Here's a link to it: cloudconvert.com/mp3-converterWe suggest you set the bit rate to 128 kbps. This tool can also increase or decrease the volume for you if you need to change the volume of the original file. Additionally, you can tell it to trim audio off the end of the file if you have extra audio dead space you need to get rid of.After using the tool, just save the mp3 file to your computer and then transfer it to the controllers memory as directed in the user guide. Of course, please feel free to contact us if you need additional assistance.