A harmonizer automatically plays additional "harmony" notes along with the guitar, given a certain key and mode, allowing the guitarist to effectively play multiple parts at once.
Placed on the Pumpkins' official eBay account on 2011/12/01, ending on 2011/12/11 at $800. The accompanying text read:
Digitech DHP-55 Five Part Digital Harmony Processor. Used by Billy Corgan on the 1995-1997 Mellon Collie and the Infinite Sadness album and tour. The unit includes Billy Corgan's settings for the following songs: Hummer, Cherub Rock, Drown, Soma, Rocket, and Today. The unit has been kept in a smoke-free studio environment. No cables or manuals are included. A certificate of authenticity will be included. Unit is sold "as is".