Charles Ives' 3 Quarter Tone Pieces (1924)

Below are Anthony and Joseph Paratore playing the 3 Quarter Tone Pieces of Charles Ives. The second piano is tuned a quarter tone lower than regular pitch. The reason for tuning lower rather than higher? Tuning a piano a full quarter tone higher than 440 might add too much pressure to the piano's mechanism, possibly damaging it. Tuning lower causes no damage other than the bill you'll get in order for the technician to return the piano to 440 after the concert.

Listening to this piece in the 1920's must have been like setting foot on another planet. I like Accisma's comment:

You serve the meal to your guests, and sit back anxiously. Their response is.. not similar to your own. They gag, choke, grab for the water, some even vomiting. They then proceed to hurl abuse in your direction, accusing you of feeding them something that isn't even edible.

It would be hard to defend yourself without sounding like you're an elitist. To us, it really does feel like people are missing out on something amazingly beautiful, an aesthetic sensation like no other.