List of sounds that got changed:
SMG (shooting/reloading)
Shotgun (shooting/reloading+cocking)
Semi-auto rifle (shooting/reloading)
Empty chamber sound
Bullet impact (iron/common blocks)
Grenade bounce
Explosion sound
Intro music
Maybe I will change other sounds too, like walking, building, death sounds etc. I will update the post if it happens.
Track I used to make intro.wav: