http://mojang.com/2016/03/minecraft-191-pre-release-1/
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Update: Minecraft 1.9.1 Pre-Release 2 is now available.
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Elytra sounds are now ready, so we bundled them with a few bug fixes and
decided to make a Minecraft 1.9.1 pre-release available for everyone to test
these changes.
Most of us are going to San Francisco next week to attend GDC, so we will
release Minecraft 1.9.1 in two weeks.
Notable changes:
Added Elytra sound effects
Improved AI
Improved entity selectors
Tweaked cooldown mechanics to be less confusing
Applied paper patch 0078
Loot tables now also work in dispensers and droppers
Hoppers can now pull items out of blocked chests
Increased limit for “executed command blocks per tick”
Bugs fixed:
[Bug MC-56162] - Worldborder damage 0
[Bug MC-96219] - Block Duplication Bug with Pistons (ghost blocks)
[Bug MC-98327] - Elytra texture transparency issues