Ryan says:

There's a thread over at Metafilter discussing The Unheard Beethoven - a site devoted to unrecorded/unperformed Beethoven pieces.

Even though Deutsch Gramophone released a 'Complete' Beethoven Edition series in 1997, there still remains a healthy chunk still neglected.

Once I stumbled upon this mini-rabbit hole, I was surprised that a revised, 1822 edition of Fuer Elise exists - the popular version around today was done in 1808. Seems that ol' Ludwig von wanted to spice it up, or couldn't get Schubert to attempt a glitch remix of it, or add it to a series of Bagatelles. Fast-forward 170+ years to Modern English's rerelease of 'I Melt With You' with added synth part - coincidence?!?!?!!? (??)

Here be a link to a MIDI & explanation to the 1822 version. For those of you who have 'MIDI aversion syndrome' *raises hand*, it's actually not that bad.