So, I demo a lot of gear and also spend a lot of time inspecting / tuning things using music. Unlike a typical audio reviewer, I find that songs with difficult / problematic audio help me evaluate the performance and FR of a given device. A well mixed and wonderful-sounding recording tends not to make problems with the gear very apparent in my experience. For example, the track The Rub Off by Plump DJs basically uses a series of clicks as a major part of the bassline. Even worse, they apparently rectify the signal so that it's unipolar - rather than pushing the speaker in and out, the speaker will (theoretically) only move outwards. This weird audio makes for a great stress test. You can tell something about FR as well as dynamics right away when you listen to this song. (it's also a song that suffers terribly from low bitrate lossy compression, but that's another thread...) Another good example is the original recording of Holy Ghost by the Bar-Kays. Although there is a really deep synth bass throughout the track, it's mixed in such a way that it sounds very weak and distant if your speakers / headphones don't have excellent bass extension. Even if they do, it doesn't exactly jump out of the mix. So by listening to this I know within seconds where we're at with sub-bass. So, I am wondering if anyone else has "defective" songs that are good for quickly identifying the behavior of a speaker or headphone?