There are only 81 possible Parsons Codes for a 4-chord song.
I should've said that a naive version of it would be easy (like a channel-wise, instrument-wise, or track-wise code).
i forgot to mention that it's a completely different format - but it shows what's needed for such a parser.
Most people can't pick out intervals by ear, but they can manage "higher" "lower" or "the same".
Sure there's a possibility to identify a completely different song, but the more notes given, the smaller the chance to coincidentally find two different songs with the exact same ups/downs/repeats.