XDR and cassette tapes

If you bought a cassette tape in the 1980s or 1990s, and it was made by Capitol/EMI (such as the British Beatles or the allegedly Irish "McHammer"), it probably had an "XDR" logo on it.  That was a system of improvements in the production chain to create better-sounding tapes.  A small side-effect was that the dubbing equipment added a set of test tones at the top of each side.  These are tattooed on my brain, and now you can enjoy them, too.