Defender was Williams Electronics' first video game; they had previously produced only pinball machines. The sound effects in Defender came from the company's earlier pinball games, most notably Firepower.
The NES adaptation of Defender II borrowed a few sounds and songs from Punch-Out!!. The title screen tune of Defender II is the "begin round" music from Punch-Out, albeit with a Star Wars-esque flourish at the end. The tune that plays when you win a round in Defender II is the music that plays when you lose a match in Punch-Out. Lastly, and much more subtly, the sound of enemies exploding in Defender II is one of the sound effects that plays when an opponent in Punch-Out is knocked down. Nintendo had a hand in the development of the NES port (see below).
The Shelf of Movie Languishment: The NES adaptation of Defender II (as well as Joust and Millipede) had been co-developed by Nintendo and HAL Laboratory in 1983. They were meant to be part of the deal Atari had with Nintendo distribute the Famicom outside of Japan, but after a confluence of factors related to The Great Video Game Crash of 1983 killed the deal, HAL published the game by themselves in 1987, four years later.
" by Sheena Easton. At the bridge of the song, Sheena drops the machine over the balcony. Even in The '80s, never ditch your girlfriend over video games.