At the end of the Beatles' song "A Day in the Life," an ultrasonic whistle, audible only to dogs, was recorded by Paul McCartney for his old English sheepdog "Martha". Try it out on your pooch and see what kind of reaction you get.
Following "A Day in the Life" on the Sgt. Pepper album (as first released on LP in the UK and years later worldwide on CD) is a high frequency 15 kilohertz tone and some randomly spliced Beatles studio chatter. The frequency is best understood as what you would know as a dog whistle as the frequency is only picked up by a dog's ear.