Why not just use John Chambers' tunefinder
Yes, that's good for finding trad ABCs on the net. But, for example, I've created a number of large custom ABC collections on my HD that are not out there. One contains the exact settings I play and personal variations I've created. Another contains my note-for-note detailed transcriptions of recorded tracks. Another contains non-ITM, such as symphonic theme incipits I've written down. JC ain't gonna help me with those.
Plus, if you want to find every E Dorian reel with a roll in the 3rd bar, and that ends on a note other than the tonic, you need something like grep or Perl regexes to construct a complex query like that. And success will depend partly on a consistent, uniform formatting of the ABCs*, of which there's definitely no guarantee by grabbing something off the net. For that you want your own selected ABC collection and search tool.
* This is why I usually check the Norbeck collection first. Because his formatting and transcription conventions are very consistent and predictable.