Accordianism is a sect of Discordianism founded by Father Nemo Proprius. Accordianism is "Discordianism according to [Father Nemo Proprius]".
Accordian's generally believe in all the same things as other Discordians when it's convenient. Notable exceptions are the Law of 25s as discovered by FNP, and the Law of fours, discovered by Padre Quadrapoonia.
"Discordian: an out of tune accordian." ~Reverend Loveshade