MP4 to M4A for Music Production

Keep M4A out of the session itself. Lossy files inside a project mean the DAW decodes on import and re-encodes on export, and any processing you apply — EQ, compression, limiting — amplifies the codec's artifacts rather than hiding them. M4A is a delivery format: reference mixes, client sends, demos on a phone.

One trap catches people out: lossy encoding can push peaks slightly above the source, so a mix sitting exactly at 0 dBFS can clip once it becomes a M4A. Leave about -1 dBTP of headroom on the bounce you encode from — standard practice for masters, and it applies to reference files too.

Never send a lossy file to a distributor or streaming platform. They transcode whatever you upload into their own formats, so handing them an already-compressed file stacks a second lossy generation onto what your listeners actually hear. Deliver lossless; convert to lossy for humans.

Storage-wise you're looking at about 50× less: 60 MB per minute becomes roughly 1.2. MP4 already discarded data; M4A will discard a little more. Pick 192–320 kbps and it won't be audible in normal listening.

The MP4 on your drive almost certainly started life in phone video, and the video stream is nearly the entire file, so extracting the audio collapses a 500 MB video into a few MB. M4A is the destination because it plays essentially everywhere — iPhone Voice Memos and every ordinary phone, browser, and player. A minute of MP4 is about 60 MB; the same minute as M4A is roughly 1.2. Across an album or a long recording that difference decides whether it fits on a phone. Both MP4 and M4A are lossy, so this pair stacks a second encode — at a generous bitrate it stays inaudible, but if a lossless original of the MP4 exists, encode the M4A from that instead.