"Welcome to the Machine", by Pink Floyd, is a song featured in the Person of Interest episode “YHWH”. It is played at the end of the episode when the crippled Machine sends Harold a message on a laptop, calling Harold "Father" and apologizing for failing him.
"Welcome to the Machine" appears on the seminal Pink Floyd album, "Wish You Were Here," which is widely considered among the greatest rock albums of all time. The song tells the story of an aspiring young musician, whose experiences serve as a metaphor for the band's growing disillusionment with the money-making aspects of the recording industry, which took priority over creativity and artistic expression.
Welcome my son, welcome to the machine