Cassette tapes were invented in 1967 by Phillips to improve the usefulness of recorded sound. A tape recorder can record and replay voices and music on tapes, which contain set lengths of magnetic tape. Stereo tracks are recorded on each side of the tape. Once the tape is inserted into the machine the tape spools fit over the spindles. Once play is pressed the playback head is pushed against the tape. The rubbing against the playback head and produces an electromagnet pulse. The tape moves against the head and either records or plays sounds due to the electromagnet rearranging the particles or disorientating the particles in the case of recording.