Favorite song to demo or test drive speakers?

The whole Emmylou Harris album "Cowgirl's Prayer" with it's goods and bads.

As a sidenote important to test the capability of a system on modern R'n'B and electronic. Very demanding from 15-20 000 Hz. Kills Harbeht's :-)

A Great topic,
Among others, iI use Herbie Hancock, River The Joni letters track two Edith and the Kingpin, featuring  Tina Turner, Wayne Shorter etc, beautifully recorded with many complex layers , subtle bass it really sorts out how well my speakers are placed and how well a streamer can recreate the various instruments timbre and placement and clarity. Infact the whole album is good for this but track 2 is my favourite I guess thats why the albumn won the top Grammy award in 2007

Chuck Mangione  -  FEELS SO GOOD

Fleetwood Mac Dreams
Donald Fagen:  Tomorrow's Girls
Dire Straits:  Six Blade Knife
Also for newer music:  Zhu, Post Malone. 

Motorhead used Back in Black to soundcheck equipment, and if it's good enough for Motorhead, it's good enough for me.
But I would also add Dire Straits' debut and Neil Young's Harvest.