EDITED TO ADD:
It works quite well, presenting you in the top left-hand corner with a representation of a two octave keyboard. Melodies are normalised to start on A (so if you feed it something with a starting note of E flat, you disconcertingly see it transposed up an augmented fourth on the read-out to the right, but that’s not really a problem).
Once you’ve added your melody and clicked the search button, you’re presented with a time graph* with an oscilloscope-like tracing of search results over that continuum, and some links to narrow in on a given time band. So say you enter Eb2 G2 Eb2 Bb1 Eb2 G2 Bb2 Eb2 and click search, then you find a big spike around the year 1803, with a number of much smaller spikes all the way back to 1698 and forward to 2008. The result for 1803 links to about 7 different IMSLP scores by page number (as well as providing the obligatory EweToob link).
It knows the repertoire quite well. I fed it a few peculiar examples designed to trick it, and surprisingly it didn’t always fail. Angular melodies are much more easily detected than ones that move by step; it took about three or four different melodies from a piece by Schönberg before it could grab the correct piece. Beethoven’s 5th is easily found (though the last movement theme also picks up some Mozart with similarities!) The L’homme armé tune (either the major or minor version) fails dreadfully. It even knows some of my own pieces**. But it didn’t identify the piece of Bach
in a recent discussion when given the first 9 notes (which have an ambit of an octave).
If I have a criticism, it is that the scaling of the time graph is often too narrow or wide for the number of results, and there doesn’t seem to be a way to alter that. Based on the melodic search, you’re given several time intervals to investigate, and some are too narrow while others are too wide; as the results are date sorted, if the search picks up a huge number of results and you know the one you want is almost at the end of the interval, then you have to click through screen after screen of “Next” results. Especially as the time graph clearly ranks some results much higher than others, it would be preferable to have the first screen report the highest-ranking results, and subsequent screens could then list the remainder chronologically.
Executive summary: a very useful tool!
* Going all the way back to 1198… I wonder if my datings for Pérotin’s conductus pieces Viderunt omnes and Sederunt might have a bearing on that? (Yes!)
** I fed it motifs from Opp. 1 and 5 which it successfully found.