According to FFShrine, the missing numbers have been found:
snd_bgm_X12_SIMPLEINTRO (Classic Mode Intro)
snd_bgm_X14_ENDING (Classic Mode Ending)
snd_bgm_X24_HOW2PLAY (How to Play)
snd_bgm_A11_MLRPG02 (Another piece from one of the Mario & Luigi RPGs)
snd_bgm_A12_MORINOKINOKO ("Mori no kinoko" = Mushroom Forest...which game? Could it be...SMRPG?!)
snd_bgm_C06_KAZENOSAKANA (Ballad of the Windfish)
snd_bgm_E04_COOKIE (Yoshi's Cookie)
snd_bgm_G06_COMMAND (Star Fox: Command)
snd_bgm_J01_STAGECHANGE (No idea...maybe BGM for when Castle Siege changes forms?)
snd_bgm_J05_ERABARESHI (Erabareshimono = "The Chosen One(s)")
snd_bgm_K02_SENTOUONIISAN (Battle with Masked Man from MOTHER 3)
snd_bgm_K03_EIGHTMELODIES (Eight Melodies from EarthBound)
snd_bgm_K04_SMILEANDTEARS (Smiles and Tears from EarthBound)
snd_bgm_K06_BECAUSE (Because I Love You from EarthBound)
snd_bgm_M14_WARIOSTAGE (Another Microgame$ tune)
snd_bgm_N04_RADIOTAISO ("Radio Taisou" = Radio Exercises)
snd_bgm_Q03_SPORTSMEDLEY (Soccer / Baseball / etc. on the NES, probably)
snd_bgm_R01_WILDTRACKS (No clue...)
snd_bgm_S01_MAINTHEME (MGS Main Theme...no doubt taken out of the main game because of the composition controversy)
snd_bgm_S09_BEATMANIA (MGS music from Beatmania?)
snd_bgm_T04_HOWTOPLAY (Original "How to Play" music?)
snd_bgm_U05_UCANDO ("You Can Do It"...? Probably another vocal track.)
snd_bgm_W22_DX55 (The missing Melee track...Fourside?)
snd_bgm_Y06_ADV06 (Missing Subspace Emissary music)
snd_bgm_Y12_ADV12 (Missing Subspace Emissary music)
snd_bgm_Y18_ADV18 (Missing Subspace Emissary music)
snd_bgm_Y19_ADV19 (Missing Subspace Emissary music)
snd_bgm_Y20_ADV20 (Missing Subspace Emissary music)
snd_bgm_Y21_ADV21 (Missing Subspace Emissary music)
snd_bgm_Y22_ADV22 (Missing Subspace Emissary music)
snd_bgm_Y23_ADV23 (Missing Subspace Emissary music)
snd_bgm_Y24_ADV24 (Missing Subspace Emissary music)
snd_bgm_Y25_ADV25 (Missing Subspace Emissary music)
snd_bgm_Y26_ADV26 (Missing Subspace Emissary music)
snd_bgm_Y27_ADV27 (Missing Subspace Emissary music)
snd_bgm_Y28_ADV28 (Missing Subspace Emissary music)
snd_bgm_Y29_ADV29 (Missing Subspace Emissary music)
snd_bgm_Y30_ADV30 (Missing Subspace Emissary music)
snd_bgm_Z09_FLUIGI (Luigi's Victory Theme)
snd_bgm_Z12_FKUOPA (Bowser's Victory Theme)
snd_bgm_Z13_FPEACH (Peach's Victory Theme)
snd_bgm_Z14_FZELDA (Zelda's Victory Theme)
snd_bgm_Z15_FSHEIK (Sheik's Victory Theme)
snd_bgm_Z19_FFALCO (Falco's Victory Theme)
snd_bgm_Z20_FGANON (Ganondorf's Victory Theme)
snd_bgm_Z24_FZEROSAMUS (ZSS's Victory Theme)
snd_bgm_Z26_FLUCAS (Lucas' Victory Theme)
snd_bgm_Z27_FDIDDY (Diddy's Victory Theme)
snd_bgm_Z28_FPOKETRAINER (Pokemon Trainer's Victory Theme)
snd_bgm_Z32_FDEDEDE (King Dedede's Victory Theme)
snd_bgm_Z33_FLICARIO (Lucario's Victory Theme)
snd_bgm_Z34_FIKE (Ike's Victory Theme)
snd_bgm_Z37_FPURIN (Jigglypuff's Victory Theme)
snd_bgm_Z38_FMYU2 (Mewtwo's Victory Theme)
snd_bgm_Z39_FROY (Roy's Victory Theme)
snd_bgm_Z41_FTOONLINK (Toon Link's Victory Theme)
snd_bgm_Z52_JCLEAR1 (Some accomplishment music...probably for clearing a stage / event)
snd_bgm_Z53_JCLEAR2 (More accomplishment music)
forums.ffshrine.org/showthread.php?t=49628&page=91Makes me sad to see Yoshi Cooke content as well as all that glorious Mother music cut... And The Ballad of the Wind Fish! Gah