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 2500 and 3500Hz 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?