Are these Tags important or can I delete these?

HI.

I recently took the Time to organize and clean my MP3-Collection and I noticed there are a lot of Tags in some of them that I didn't put there. And now I'm wondering if I can delete these without destroying anything.

These Tags are:
AUDIOCHANNELS
COMMENT ITUNES_CDDB_1
COMMENT ITUNES_CDDB_IDS
COMMENT ITUNES_CDDB_TRACKNUMBER
COMMENT ITUNNORM
COMMENT ITUNPGAP
COMMENT ITUNSMPB
COMMENT MUSICMATCH_BIO
COMMENT MUSICMATCH_MOOD
COMMENT MUSICMATCH_TEMPO
COMPATIBLE_BRANDS
DESCRIPTION
ENCODEDBY
ENCODER_SETTINGS
ENCODERSETTINGS
ENCODING TIME
ENCODINGTIME
FILETYPE
ITUNMOVI
ITUNNORM
ITUNSMPB
MAJOR_BRAND
MINOR_VERSION
MOOVPOSITION
PURCHASE DATE
PURL
RIPPING TOOL
SOFTWARE
TAGGING TIME
UNIQUEFILEID

And there are also hese Tags:
REPLAYGAIN_ALBUM_GAIN
REPLAYGAIN_ALBUM_PEAK
REPLAYGAIN_TRACK_GAIN
REPLAYGAIN_TRACK_PEAK

I thought MP3Gain doesn't write ID3-Tags.

Thanks in advance for any help!

I would compare the list of fields with the list of fields that are supported by MP3tag:


and then keep only those that match.
All others are most likely user-defined fields and/or typical to one player which means that other players probably cannot benefit from these fields (i.e. ignore them) which means that no harm will be done.

I would say it is not a matter of "destroying" anything. If you delete such a tag, the music itself will not be touched.

It's more a question which programs do you really use (iTunes? MusicMatch? Mp3Gain? Ripping and Encoding tools?).
Example:
If you want to adjust the loudness of your songs, you need the information in the REPLAYGAIN tags. But you also need a player software capable to read and process them. If you don't care about Replaygain, you can delete this tags.