If there is a piece of music that's exactly 60:00 minutes — an hour — long, then you know that duration of time has elapsed when it's done. Repeated listenings would make this more acute. And if you happen to have several such pieces of music, then you could chain them, end-to-end. This is most effective when you don't disrupt the momentum of the music (e.g., take a break). For even greater flexibility, markers could be placed within the piece to divide it into smaller increments, such as:
"Ah! The brassy horn stabs! I know half an hour has passed."
This grew out of a thought that came to me when I was listening to the radio while driving and quickly caught on to the durations of each song. Radio singles are often 3-4 minutes, sometimes shorter, rarely longer, and by knowing how many songs had played (and even better, which specific songs), I was able to mark the time I'd spent on the road.
Is there a computer program that can take a folder full of MP3s and calculate how many, and which ones are needed to make up a certain interval of time? I'd like to find this, and create mixes that go an hour — as close as I can get it. Thanks to the creative wonders of technology, time-stretching is also a possibility.
Some say they have measured their lives in coffee spoons, but I believe music to be just as potent, if even more practical.

{ 6 comments… read them below or add one }
I have worked for a local radio station in the past, I was in charge of the music computer. We had software running that played songs at random in a category, but did calculate them to fill up the hour precisely. So I can confirm such software exists.
i don't know about software, but some years at the radio made me do it by instinct. Though I am not sure how long it would take to get back into that state again.
When I was doing my undergrad in Music Ed, we used to have a yearly "Prism Concert" which took an hour from start to finish, utilized all music ensembles, and all parts of the theatre.
I love this idea of specific mixes to mark the passing of time!
@Daed: Intriguing. I like to wonder about those kinds of "vertical needs" in the computer industry, functionality important to a certain field but tends to generate "Why do you want to do that?" from casual bystanders.
@dandellion: Glad to also hear you've had in-air experience.
@Ipenda: That is pretty neat, why was it called "Prism"?
In fact, there is a song almost exactly 60 minutes long: Amarok, by Mike Oldfield. 60:04, i think, but those :04 are not that big a deal, i think….
Give it a listen, it's amazingly interesting experience. Especially after couple of times.
@Ringo: OMG I'M SUCH A BIG FAN OF THAT WHOLE TRACK! I LOVE THE ENDING, IT'S EPIC AND UPLIFTING! Glad you namedropped it… *h-h-h-haaaappy?*