This app was mentioned in 4 comments, with an average of 1.50 upvotes
Well, MODs can sound worse if the individual sample quality is low, but file size doesn't depend on playing time, since it's a midi-like structure with digital samples bundled in one file. So if one use the same samples one can have more songs for all the dungeon sections in one file. Of course a MOD, or more likely the more modern S3M, XM or IT file with lots good quality samples could be larger than an MP3, though.
If you want to listen to some of them, you can get and play them on modarchive.org . This is one of my favorites.
There are mod players for android - I use Xmp Mod Player
I was actually about to say Protracker until I realised what sub I was in, and figured you wanted torrent trackers!
I use the Protracker 2 clone on desktop and XMP Mod Player on Android.
i don't know what formats bubbleUPNP supports. i don't think it supports those.
https://play.google.com/store/apps/details?id=org.helllabs.android.xmp&hl=en
i've used this one before. it's also on f-droid
What were the .mod files meant to be used in?
Every instance of .mod files I've ever come across were [Music Tracker](https://en.wikipedia.org/wiki/Tracker_(music_software\)) files.
XMPlay will let you convert them to .mp3, Xmp Mod Player will let you listen to them without transcoding on an Android device.