During and following "Star Trek", Nimoy also released five albums of musical vocal recordings on Dot Records. On his first album, "Mr. Spock's Music from Outer Space", and half of his second album "Two Sides of Leonard Nimoy", science fiction-themed songs are featured where Nimoy sings as Spock. On his final three albums, he sings popular folk songs of the era and cover versions of popular songs, such as "Proud Mary" and Johnny Cash's "I Walk the Line". There are also several songs on the later albums that were written or co-written by Nimoy. He described how his recording career got started: