This non-profit site aims to be especially useful for both experienced and novice players of traditional Irish music as well as for musicologists. It appears to be unique in the world for its coverage of recorded sources of Irish traditional music. At this point in time, the site offers you at least the following uses:
Locate commercial recordings of a tune, given any one of its titles.
Locate transcriptions of a tune in a book, given any one of its titles.
Discover whether the tune you are listening to or looking at is known under other titles.
Find out whether multiple tunes recorded or printed under a given title are actually the same tune or not.
Identify unnamed tunes on a recording. Every tune indexed here can be found even if you only know the track title, such as "Sliabh Luachra Polkas" or "Light Jigs." Just use the Tune Search and Finder page to search for the track title.
View a more accurate table of contents of your recordings. I have discovered that a significant fraction of commercial albums have inexcusable errors in labeling their tracks and tunes, especially due to non-musicians being responsible for preparing the albums and their later reissues.
Build custom-fit tune sets for set dancing, by using the bar counts given for most of the dance tunes.
Build tune sets based on key changes, by using the mode identifications given for most tunes.
For more Frequently Asked Questions go to the FAQ page.
Other Tune Indexes on the Web
Besides this site, there are also other kinds of tune indexes available. First the recording indexes:
The only similar index, in either printed or electronic form, is Andrew Kuntz's The Fiddler's Companion. I recommend it if you are curious about the broad history behind a tune. It apparently uses a data structure similar to mine, but very different data. His sources are primarily printed transcriptions rather than recordings, he combines Irish with non-Irish tunes and musical concepts, and some of his basic principles are quite different. My plans for what I hope to release eventually from my private database are similar in scope (regarding magnitude of information per tune) but quite different in format and content.
Jane Keefer has also published a useful database as Folk Music: An Index to Recorded Resources. It is primarily focused on American music, but includes some Irish sources. Cross references are sometimes included.
Occasionally you can find a variety of sources and anecdotes about tunes by searching the IRTRAD-L archives.
You can also try thesession.org, which is a community-written collection of mostly Irish tune information. You may find interesting anecdotes about tunes here, but since nobody ever sorts out which tune people are actually intending to write about, it's often quite a jumble. For example, utterly unrelated tunes are talked about as one tune just because somebody thought they had similar tune titles!
Rod Stradling's "A Discography of Recorded Traditional Music," although not focused on Irish nor on tunes, includes so many valuable sources of Irish tunes (with album reviews!) that it deserves recommendation here.
Gerard Manning's Ceolas site kindly maintains links to other indexes of printed tunes. James Stewart's TuneIndex, the largest of them, has been claimed to be a cross-referencing index, but in fact it depends entirely on similarity of tune names for its cross-references, which is highly insufficient and often misleading. Read especially the "Title" section of Stewart's interesting "Introduction" for confirmation of this from Stewart himself. Try also the updated (>70,000 tune instances) and downloadable (but not as searchable) edition of Stewart's index.
Paul de Grae has generously shared his careful, properly cross-indexed index of Irish tune books. Thus you can find the same tune in various books regardless of whatever titles the books used.
"Cantaria is a library of traditional and contemporary folk songs, mostly from Ireland, Scotland, and England."
The "Digital Tradition Folk Song Database," hosted by Mudcat Café, is a very large collection of information contributed by anyone in the world, sometimes including experts, about folk songs, including many Irish songs.
For book publications of cross-referenced tune indexes, see CRE and FF in the Bibliography.
For other recommended Web sites about Irish traditional music and other "Celtic" traditions, see my link collection at the Celtic Music Association of Madison, Wisconsin.
Note that "traditional Irish music" is another order of words to use in Web searches.