Crop the parts you don't like out of your music files.
Download audacity. Just agree with the install. It's fairly easy to use.
Open your mp3 and find the part you don't like. I changed the start/end/position at bottom of screen to just display number of elapsed seconds, then found the positions I wanted as start/end by observing current position as it played, then manually typed them in. To crop, just specify a selection and use: Edit > Remove Audio > Delete. Then to save the changes use File > Export.
Then when exporting to mp3 for the first time, just browse to the installed dll. C:\Program Files\Lame For Audacity\lame_enc.dll
My source mp3 was:
Duration: 7:45 Bit Rate: 256kbps Channels: 2 (stereo) Sample Rage: 44 kHz Size: 14.2 MB
My cropped file using all defaults during export was:
Duration: 4.59 Bit Rate: 128kbps Channels: 2 (stereo) Sample Rage: 44 kHz Size: 4.57 MB
That means reduced quality. That's fixed by: File > Export > Options > Quality: 256 kbps, which resulted in:
Duration: 4:59 Bit Rate: 256kbps Channels: 2 (stereo) Sample Rage: 44 kHz Size: 9.15 MB
Another problem I have is files whose majority is too quiet to hear at the volume at which I normally listen. Simple amplification won't help if there are some loud peaks, as these will either be clipped or prevent proper applification. The solution is audacity's compressor effect which squashes the peaks then amplifies the track. I just successfully used it with the following settings.
Threshold: -15db Noise Floor: -40db Radio: 5:1 Attack Time: 0.1s Decay Time: 1.0s