You will need some background or dancing music. You will need some Christmas jingles for the Christmas party. Spooky sounds and horrifying tunes for the Halloween bash. Some rock songs for the more hip crowd. Country just because it is your favorite.
CD players can do the trick.
Cassette players are another alternative. You can even make up a cassette of your own. You could rent a karaoke machine, or hire your favorite disc jockey to keep the group entertained. Now you will have to purchase some party invitations and put them in the mail at least four weeks in advance. When deciding what type of invitations to buy, keep in mind, that even if the store has a nice selection of theme invites, you also have other options.