Editing Songs' Volumes

What software do y'all use to edit your music library's songs' volumes?  I used to have my library on iTunes which had that option though now that I switched to Sony, I can no longer edit songs' volumes.  And now some tracks are super quiet while others are loud.  Is there a recommended free software or way to easily change this?  I'm running Windows.  Thanks!

I used to use Audacity when I would record cassettes to MP3 files, its a pretty easy to use sound editing program, that allows you to louden the tracks

https://www.audacityteam.org/download/

Thanks dude!  Ah this is the program I was trying to remember the name of.  Downloading now.  

Yep that's the one I use when converting LP records to digital.

Right on.  I'm running into an issue here though...  I just got a new CD and it's pretty quiet compared to the rest of my library.  When I go into Audacity to edit the songs (using the "amplify" tool which according to some guy on youtube, is the tool to use for this), the tracks' peaks are already at their maxes, i.e. if I were to "amplify" them, i'd be cutting out the high notes.  I just want the playback volume to be louder...  Is there another tool within Audacity to fix this?  Thanks!

Ok I think I gotta adjust the "gain" which is easy enough, though in Audacity can you only "export" to a new file?  That'll require re-linking everything I adjust in my music library and such.  I'd rather just edit the file in place instead of creating a new one...  Thanks!

Yep, export to a new file then delete the old ones. Normally what I do is track one side of an album as one file, then I edit each song out of that track to create individual tracks. Be sure to set up Audacity at 320 kbps.

Ah dang, that'll be a lot of work - especially for albums with a bunch of songs.  I am really starting to miss iTunes because they made it so easy!