I have a couple SACD's both by Blood Sweat and Tears Vol 2 &3.
Awesome sounding SACD's.

ozzy
If I'm limited to 1 album it would be a 'Book of Roses' by Andreas Vollenweider. It contains instruments that highlight all aspects of a system including harp (including some deep bass notes on the harp that many systems can't reproduce), piano, acoustic & steel guitar, flute and acapella vocals. Vollenweider is also famous for creating rhythmic percussion by playing chalk on a chalkboard, the sound of tumbling marbles and book pages being turned. This really helps evaluate a system as we all know what these common household items sound like.  

I agree with many of you on choices such as Blood Sweat & Tears, Beck (especially the Morning Phase album) and Al Dimeola's ' Flesh on Flesh' album. Other notable tracks include 'If You Go' by Shirley Horn for the unbelievable recording of vocals, piano and drums, especially the cymbal work and 'She's Already Made Up Her Mind' by Lyle Lovett.
The best songs to test your speakers on are the songs you will listen to once you have chosen your speakers.

Case in point........

From another op...

Listening to mostly jazz, solo instruments and vocals I find my Martin Logan Spire hybrids to sound awesome, but recently I was listening to some both "Busy" 90’s rock and classical (lots of instruments playing loudly together) and I find the music starts to sound garbled and annoying (to bright), so much so, I turn it off.
I was wondering if you all might have some suggestions on some speakers that would be a little more forgiving with busy/loud music that I could possibly switch over to when listening to different types of music. That is unless I can find speakers that can handle all styles of music, then I would consider taking the hit ($$$) on selling the Spires.

Without getting into room size and dynamics, lets just call it a standard room, I was also looking for something more efficient. The Spires need a huge amount of power (and volume) to sound good. Looking more for something I can listen to loud but also still enjoy the music at a much lower volume if that’s at all possible. Neutral and not to bright.
Living in the sticks, I can’t just jump in the car to go demo speakers. Only once, in the past, did I purchase a set of speakers online and unheard, going solely on the sales person’s recommendations. I learned the hard way to never do that again!

Equipment now: Coda CSiB integrated amp with W4S 2v2 SE Dac running Roon Nucleus.

I also wanted to mention that the Spires have phenomenal base, so much so I sold the 2 subs I was originally using with them. Floor standers and bookshelfs have come along way in SQ these days, but if I need to purchase another set of subs the budget is starting to dwindle.

I find it best to listen to a variety of music that is well recorded, well listened favorites. I burned a CD that I used (and continue to use) for auditions. Some show soundstaging, others impact, etc.

I left out classical even though I own a number of pieces but don't listen as often as I used to...

Shirley Horn - The Music That Makes Me Dance
Rebecca Pidgeon - Spanish Harlem
Michael Franks - Dragonfly Summer
Dianne Reeves - Never Too Far
Fourplay - 101 Eastbound
Steely Dan - Jack of Speed
Grace Jones- Don't Cry - It's Only The Rhythm
Larry Carlton & Lee Ritenour - Take That
Herbie Hancock - Butterfly
Lee Ritenour - Boss City
Dave Brubeck - Take Five
Miles Davis - So What
Buddy Guy - Sweet Black Angel (Black Angel Blues)
Cassandra Wilson - A Little Warm Death
Troubles What you’re in - -Fink (Live from Union chapel London)
Keith Dont Go - Nils Lofgren
Daggers & Knives - Woodes
Hey Now - London Grammar
Caught our in the rain (live royal Albert hall ) - Beth Hart
Mountain Time (Live at Carnegie Hall) - Joe Bonamassa
Serious - Bernard Allison
River Child (acoustic ) - Civil Twilight 
Heaven I know - Gordi 
Parade of the dead (unplugged) - Black Label Society
Blessings & Curses - Wolves at the gate
Euphoria - Stalgia
Mindlessness - Jimmy Wahlsteen

Lots of different types of music to hear - full soundstage, crisp vocals, a punch is bass, the feeling like the artists are actually in the room with you. If these don’t sound great on your system you need to replace it. Lol