Music Disc

Music Discs (previously named Records) are items added in Alpha 1.0.14 that can be played in jukeboxes. They play music made by C418. It has been stated that in the future, there will be 14 music discs to find in Minecraft. Despite the music files themselves being saved in a playable .ogg format, custom music cannot be used unless a modification is installed. The Changelog for 1.6 confirmed that the record player will support 'more than 15 songs.' In Beta 1.9 Pre-release 2, 9 new discs were implemented.

Acquiring Discs
The Music Discs "13" and "cat" are found in 8% of dungeon chests and are also dropped when a Creeper is killed by a Skeleton's arrow. After the 15 December 2011 snapshot (11w50a), all discs except "11" could be dropped by Creepers.

The player can achieve this by positioning a creeper between a Skeleton and themselves, then attracting the Skeleton's fire. The Creeper will target the Skeleton once damaged by it, so the player should make sure the Creeper is near death to prevent it dying by explosion instead. Hitting a Creeper twice with an Iron Sword or four times with the Bow will leave them near enough to death for the Skeleton to make the final blow. Beta 1.5 gave all sword one half more damage, making Stone/Wooden swords ineffective for simply weakening a Creeper. The player may also trap the weakened Creeper and Skeleton in a 2x2x3 hole, then walking around the edge until the Skeleton fires and hits the Creeper. Be sure to back away if the Creeper begins to hiss.

Please note, these tracks have been shortened to 30 seconds on the wiki, due to an agreement with the author to allow them onto the wiki. This does not apply to "11".

As for Minecraft update 1.1, all of the discs can be obtained in dungeons, strongholds and dropped by Creepers killed by Skeletons.

Unused Music Files
Until Beta 1.9, Minecraft had 12 unused Music Files. After that point, only one remained unused. These are stored along with 13.mus and cat.mus (which have been decoded as 13.ogg and cat.ogg respectively). The song "where are we now" was not added in Beta 1.9 Pre-release 2 because of problems with the spaces in the name.

Trivia

 * Gold "13" music discs were noticeably more common than green "cat" ones until Beta 1.2_02, but after the Beta 1.3 update, green "cat" discs are more often dropped.
 * The 12 music tracks created for records by C418 can be found in:
 * Windows: %appdata%\.minecraft\resources\streaming\ (AppData is hidden by default)
 * Linux: ~/.minecraft/resources/streaming/ (.minecraft folder is hidden)
 * OSX: ~/Library/Application Support/minecraft/resources/streaming/ (~/Library is hidden in 10.7)
 * Of the 12, only Cat and 13 are in a readable Ogg Vorbis format. The remaining .mus files are locked with a simple encryption algorithm. However, they can be decoded by Minecraft on the fly.
 * Before Beta 1.6, an SMP bug existed when a music disc was ejected from a jukebox. The disc would pop out along with a "ghost" client side disc that only you could see. This ghost disc was not able to be picked up.
 * You can make the discs play your own music by replacing the .ogg files for "cat" and "13" with your own .ogg files.
 * There is currently a bug where if you put a music disc in a jukebox and then turn the sound off (in Minecraft options tab,) the music will continue playing, even when you eject the music disc. Regardless of how far you travel, you will hear the music until the song ends. This can be fixed by turning the sound back on, reinserting the music disc, and then ejecting the music disc.
 * C418 first announced new music discs in Beta 1.8.
 * Two music disc names are in Swedish. "Stal" means stole and "Strad" means slabs.
 * "11" is the only Music Disc that is shattered to pieces, explaining the broken noises at the end. It also appears that the barking noises may have came from a Wolf, though both sounds are different.
 * Music discs are easier to get on harder difficulties because skeleton arrows do more damage on higher difficulties.