If you listen to music via 3.5mm jack for several hours, Android may forcibly reduce loudness and this is nuts.
The only way to disable it on some devices is by editing build.prop, which is a little cumbersome to do manually (one has to also use remount, etc).
This application basically does this in 2 clicks.
Obviously, this requires root.
I hold no responsibility for any damages whatsoever, please read the code before using on production devices.