Best free Program/Website to compress music?

[EseQueL]

I am creating an android game but it's currently over the 100mb limit.
I definitely need to compress the music as it's taking up around 60mb.
I tried free online music converters but some bgm increased in size after converting them to 128 kbps and mono.
The drop in quality is also noticeable.
So as the title says... What's the best free program/website to compress a bgm?
Any suggestions for best way to compress music for mobile?

 

[Andar]

a lot of people use audacity

However, the problem you have depends on the settings given for compressions and you'll either need a good background info on that or to experiment until you found good settings - there is always a choice between size and quality, and the trick is to find settings where the quality loss is not recognizable to the player.

 

[Lithalean]

@EseQueL

What you're looking for is HE-AAC v2
(High-Efficiency Advanced Audio Coding)

(Free) X Audio Compression Toolkit (Mac OS)(@48kbs)
http://xact.scottcbrown.org/
(Paid) Fission by Rogue Amoeba (Mac OS)(@48kbs)
https://rogueamoeba.com/fission/