VCRs can also play back prerecorded tapes. But NBC and CBS refused to broadcast prerecorded radio programs. Drum machines may create sounds using analog synthesis or play prerecorded samples. Each tape is prerecorded with various musical instruments or special effects. Domain-specific synthesis concatenates prerecorded words and phrases to create complete utterances. From the early 1980s, the fidelity of prerecorded cassettes began to improve dramatically. Sometimes, live performances incorporate prerecorded sounds. However, they find the casket empty due to Joker's broadcast being prerecorded. San Francisco Opera began prerecorded video transmissions in March 2008. Prerecorded messages by Novoselic and Love were played at the memorial. Interpreting consists of many different types, such as simultaneous, live, consecutive or prerecorded. She recounted her autobiography, appeared in medleys of prerecorded songs, and interviewed Pat Boone. The show is prerecorded via a Skype conference call. Live with the band, not prerecorded tracks sitting there with earphones. Therefore, a more urgent need developed for prerecorded sound effects.