HIdden sounds in Pink Floyd's "Wish You Were Here"
This is a log-frequency-axis spectrogram of the start of Pink Floyd's "Wish You Were Here.
The vertical axis covers 9 octaves from 27.5Hz to 14080Hz.
Those bunches of parallel lines are the first solo guitar notes. But what's that diagonal line at the top, a sine tone that sweeps between X and YkHz with a period of N seconds for the duration of the piece until it breaks loose at the end? It should be audible among the higher harmonics of the guitar - maybe try listening to the piece on headphones?