Go to Preferences -> Audio -> Replay Gain mode and set it to “Album” (if you’re listening to whole albums) or “Track” (if you’re mixing it up). This will let VLC read the ReplayGain[1] tags in your files and adjust playback volume accordingly. Chances are high that a lot of your collection already has these tags, and you won’t have to do anything else. If some of your files don’t have these tags, just run a tool (https://github.com/complexlogic/rsgain for example) to generate them.

Nice! I used to do something like this, which avoids xargs altogether:

cat urls.txt | while read url; do echo download $url; done