After using MikMod and various other mod playback and editing tools on the PC with my InterWave card, I decided to start sketching out the details for my own Mod editor (aka "Tracker").
I actually got quite far, but was never motivated enough to actually start coding it. I was happy enough with existing applications, I suppose.
Recently, I have found "MilkyTracker" on my Mac, and have been very happy with that.