Back then when I make the list, I didn't include music albums unless they had some kind of games or mini games in it so probably I'm already missing much now.
I'll try to include them now so I'll add this to the list.
Gotcha no worries. Well if you do want to start tracking them, here's a list of all the ones I know about:
Today (by freezedream)Released: 2 Dec 2010
A chiptune album from Austrailian artist "freezedream", made using repurposed cartridges
https://freezedream.bandcamp.com/album/todayEternalist: A Telefuture Compilation (by Telefuture)Released: Aug 2014
A compilation album of songs from 11 artists, released on cartridge. It was only given to backers for Telefuture's "Kickstart the Future" Kickstarter campaign ($70 reward) - with only 7 of 25 claimed
https://www.kickstarter.com/projects/251446771/kickstart-the-future-of-telefuturehttps://telefuturenow.bandcamp.com/album/eternalist-a-telefuture-compilationhttp://kickstartthefuture.com/ (defunct)
Note: I'm not sure this ever saw physical production, I've never been able to find a picture of oneYM2017 (by Catskull Electronics)Original released: Jul 2017
A compilation music album with custom dot matrix VMU in a transparent cartridge.
https://catskullelectronics.com/YM2017 (defunct)
https://www.sega-16.com/forum/showthread.php?32520-YM2017-cartridge-albumRe-release: Nov 2021
Rerelease cartridge with no dot-matrix in cartridge
https://catskullelectronics.com/collections/sega/products/ym2017-reissueFuture 2612 (by TH4 D34D)Released: Jan 2018
https://cheapbeatsmusic.bandcamp.com/album/future-2612 (defunct)
http://deadstep.com/Technoptimistic (by Remute)Originally released: Mar 2019
A chiptune album from the artist "Remute", with one music video ("Red Eyes"); Standard edition comes loose (green cart), or Limited edition comes in a box with a white cart
https://remute.bandcamp.com/merch/remute-technoptimistic-sega-mega-drive-genesis-cartridgehttps://remute.bandcamp.com/merch/remute-technoptimistic-sega-mega-drive-genesis-cartridge-limited-white-edition-incl-boxRe-release: 6 Feb 2023
Rereleaese by Strictly Limited Games; boxed green cart with yellow label
https://store.strictlylimitedgames.com/products/technoptimistic-remute-mega-drive-albumhttps://www.strictlylimitedgames.com/collections/sega-mega-drive-sega-genesis/products/technoptimistic-remute-mega-drive-albumTanglewood OST (Big Evil Corporation)Released: Dec 2019
Soundtrack of the game Tanglewood, comes in an orange cartridge shell
https://tanglewoodgame.com/store/p3/tanglewood_ost_cart.htmlhttps://freezedream.bandcamp.com/album/tanglewood-ostAnalogue and Hyperdub Present: Konsolation (by Hyperdub)Released: Dec 2019
A music cartridge compilation of 11 artists from London electronic music label Hyperdub. Limited 1000-copy run, loose cartridge bundled with the Analog Mega Sg for Hyperdub's 15th anniversary. Comes in a smoky black transparent cartridge
https://www.analogue.co/editions/hyperdub-mega-sghttps://segaretro.org/Konsolationmikeyeldey: the album (by Michael Elder)Originally released: 7 May 2021
Loose black cartridge - 1st edition, limited 10-copy release
https://mikeyeldey.bandcamp.com/album/mikeyeldey-the-album-for-sega-genesishttps://mikeyeldey.itch.io/mikeyeldey-the-albumhttps://reddit.com/r/SEGAGENESIS/comments/n73v2c/i_released_my_own_game_for_the_sega_genesis_today/Re-release: 14 May 2021
Boxed pink transparent cart - rerelease, limited 20-copy re-release
https://mikeyeldey.bandcamp.com/album/mikeyeldey-the-album-for-sega-genesishttps://mikeyeldey.itch.io/mikeyeldey-the-albumhttps://reddit.com/r/SEGAGENESIS/comments/n73v2c/i_released_my_own_game_for_the_sega_genesis_today/YM2020 (by Catskull Electronics)Released: Nov 2021
https://catskullelectronics.com/collections/sega/products/ym2020mikeyeldey95 (by Michael Elder)Released: 20 May 2022
Standard edition is a gray cartridge, limited 100-copy release
https://mikeyeldey.bandcamp.com/merch/standard-edition-grey-cartridge-with-game-boxDeluxe edition is a transparent purple cartridge with CD and squishy 3D head display piece, limited 10-copy release
https://mikeyeldey.bandcamp.com/merch/deluxe-edition-purple-cartridge-with-game-box-cd-and-squishy-headOpeth Music Collection (by FlosK)Released: Aug 2022
Limited 5-copy release
https://flosk.bandcamp.com/album/opeth-music-cartridge-for-sega-genesis-mega-drivehttps://github.com/Flicksie/opeth-mega-driveDecoder (by Remute)Released: 4 Apr 2023
A chiptune album from the artist "Remute"
https://remute.bandcamp.com/album/decoder-sega-mega-drive-genesis-music-albumThere was one more, but I'm not sure it was ever printed/sold:
BlowFish (by Jredd)Released: Dec 2014
Coded by Sigflup and Kulibus1 as a demo for Datastorm 2014, featuring artwork from ZanaGB and Sigflup, and assisted by Bonefish and Linde, this album contains five tracks
https://github.com/sigflup/blowfishhttps://www.youtube.com/watch?v=jPxjPVNaMkg