I was trying to clean up my MP3 collection and was not happy. Not happy because apps claiming to remove all ID3 tags were leaving lots behind. What do geeks do when they are not happy? Yup, do it themselves! It turned out to be MUCH more difficult than I had imagined! ID3V1 are easy, they come at the end of the file and are fixed length. ID3V2 are insane, and can be many times the size of the song itself! Combine that with other re-tagging or tag removal apps doing a bad job at housekeeping and you can have some pretty broken tags. MP3 files are designed to be streamable and are buil