单项选择题

You must have heard of karaoke. Karaoke is a form of entertainment in which amateur(业余的) singers sing along with recorded music. The music is typically of a well-known song in which the voice of the original (原创的) singer is absent (不存在的) or reduced in volume. Though karaoke is popular, there are not many people who know its inventor (发明者)—Daisuke Inoue.
Daisuke Inoue is an easygoing man. He was born in the suburbs (郊区) of Osaka in 1940. At high school he took up the drums, because he says, "All you have to do is hit them." Before long he was making money as a drummer in a Hawaiian band.
By 1970, he and six partners (搭档) were playing in the clubs of nearby Kobe, accompanying (陪伴) middle-aged businessmen who sang traditional (传统的) Japanese country songs His friends, Inoue says, could all read music and so they could pick up the latest tunes (曲调). He, on the other hand, had to rely on (依靠) memory and play by following the lips of the singer as they moved. "Out of 108 club musicians in Kobe," he says, "I was the worst!"
One client, president of a small steel company, was especially fond of Inoue’s slow-follow-along style. It made the president’s bad, out-of-time singing sound much better. One evening he wanted Inoue to play for him on a trip to a hot spring resort (胜地). But Inoue was unable to leave his job.
To help out his most loyal (忠诚的) client, he decided to provide him with a tape. Inoue wouldn’t be there, but the singer would still have his accompaniment. Karaoke was born. The underlined word "they" (line 5, para.3) stand for