I had a quick review of iTunes Match and it appeared that not all my music was matched. More surprisingly, well know music ripped from Audio CD.
I decided to rerun the process with only a small bunch of music to see if this can be solved. I cleaned the iTunes local library, iCloud storage and disabled iTunes Match. Then imported the music, enabled iTunes Match and checked what happens.
My test was composed of 109 tracks from Metallica (10 albums). All of them were ripped from Audio CD using the 192Kbps rate. The result was 97 tracks matched and 12 not matched. The matched tracks are now available in 256Kbps. The unmatched tracks are still in 192Kbps. Some albums are fully matched, some have one or more unmatched tracks. I check in iTunes Store and the files do exist and have the same length.
I deleted the unmatched tracks from iTunes and iCloud, then converted the original 192Kbps MP3 tracks in WAV (Signed 32 bit PCM) format. When done, I imported the WAV file in iTunes and synced with iTunes Match. The track was converted by iTunes in 256Kbps MP3 format (at import or Match process) but the file was still unmatched. I did the same gymnastics with a 320Kbps converted MP3 ; still not recognized.
The only trick that partially worked was grabbing the CD out of dust, ripping it again and importing the MP3 file into iTunes. Some worked, some didn’t… I also did another test with an old French group CD, known in iTunes ; 2 tracks over 12 were unmatched but still referenced in iTunes Store… Something is weird in that Kingdom!