With sample playlists in hand, I was able to put together one based on my own collection of music that looks something like this:
Ramblin' Man - The Allman Brothers Band
Never Is Enough - Barenaked Ladies
Wild Honey Pie - The Beatles
I'm a Loser - The Beatles
One After 909 - Beatles
Run for Your Life - The Beatles
Norwegian Wood (This Bird Has Flown) - The Beatles
Can't Find My Way Home - Blind Faith / Eric Clapton
Subterranean Homesick Blues - Bob Dylan
From A Buick 6 - Bob Dylan
Modern Love (1999 Digital Remaster) - David Bowie
16 Military Wives - The Decemberists
The Boys of Summer - Don Henley
Man With a Mission - Don Henley
Maxine - Donald Fagen
Son of a Preacher Man - Dusty Springfield
At Last - Etta James
It's Your Thing - Isley Brothers
Feelin' Alright - Joe Cocker
One More Time - Joe Jackson
All My Love - Led Zeppelin
Custard Pie - Led Zeppelin
Boom, Like That - Mark Knopfler
Don't Crash the Ambulance - Mark Knopfler
Sunday Morning - Maroon 5
The Impression That I Get - The Mighty Mighty Bosstones
The Flyer - Nanci Griffith
Live Forever - Oasis
All Around the World or the Myth of Fingerprints - Paul Simon
The Obvious Child - Paul Simon
In Your Eyes - Peter Gabriel
Watching the Clothes - The Pretenders
Precious - Pretenders
Fat Bottomed Girls - Queen
Finest Worksong - R.E.M.
Breaking the Girl - Red Hot Chili Peppers
Give It Away - Red Hot Chili Peppers
Yertle the Turtle - The Red Hot Chili Peppers
Black Cow - Steely Dan
Hello It's Me - Todd Rundgren
Bright Side Of The Road - Van Morrison
If you noticed that this list is full of a lot of moldy oldies, you're right. But I'm of a certain age, and that's what's in my iTunes. In any event, it's not a bad list, and I have been running happily with it for several weeks. However, I quickly tire of almost anything, and longer term I would like more variety. Now, I should say that I own a lot of music. The CD rack holds about 800 discs, and it's full, and other CDs are squirreled away in various other locations. There are about 15,000 tracks in my iTunes music library, so I probably own a lot more tracks that are 90 or 180 BPM. How to find them? Ideally I'd like something that could crawl through all of my iTunes tracks, analyze the music, and automatically fill in the BPM information. I know it’s not going to be fast, but that's OK. It can run overnight if necessary, or over many nights, for that matter. I found three programs for Windows, free and commercial, that claim to do what I'm looking for.
Cadence Desktop Pro
I downloaded and installed the trial version, and my initial results were good enough that I went ahead and paid $6.99 for the full version. The problem is, it crashes... a lot. It worked well at the beginning, but after a while it became completely unusable. Apparently this happens for other people who have a lot of tracks in their iTunes library. If you have a modest collection of tracks, probably less than a thousand, Cadence Desktop Pro is a very good tool for the purpose. Otherwise, you might want to evaluate carefully before buying.
MixMeister BPM Analyzer
All in all, I like this tool. It's very fast, maybe about 5 seconds per song on my reasonably high-end developers' PC. It automatically saves the Beats Per Minute data to each track, so you could certainly use it in conjunction with smart playlists on iTunes.
BPM Detector Pro
The trial version is very limited, as you can only analyze three songs at a time. I never did figure out its scheme for exporting BPM data. According to the help file, "Source files may either be renamed, or copied to a new file with a new name. In either case the BPM value can be placed either at the beginning or at the end of the new file name." I didn't want it to do either, and fortunately it didn't create any new files, unless it put them an undisclosed location.