similitudes

I have notice some similitudes in some PF songs and also on Waters songs. In "In the flesh" live album of Roger Waters, you can hear that the intro of "Its a Miracle" have a very similar sound to the intro of "Careful with that axe, Eugene" the version of Ummagumma. And also in that same album you can hear that the guitar on "Each Small Candle" is also very similar to the guitar of "Shine On You Crazy Diamond" Part 5. About Pink Floyd, I think the acostic guitar solo of "Welcome to the Machine" and "High Hopes" are very similar. And also "One of These Days" with "Shine On You Crazy Diamond" Part 6. If you notice they start the same way. What is going on? Are they runnig out of ideas? of i am just a little bit paranoid?.

Sooner or later ideas do start to run out so previous ones get recycled. Besides, they could just be riffs that they happen to know very well, having performed them numerous times, so they use them again on another album.

Anyway the music industry thrives on older ideas. Thats why fads and phases of the music industry are always coming back in later years.