Time signatures in music are written like fractions. The numerator tells how the beats are grouped into measures. For the vast majority of Western music in every genre — popular, classical, jazz, country, etc. — this numerator is divisible by 2 or 3, but hardly ever by any other prime numbers. Musicians call exceptional time signatures “odd meters” though this is misleading. When they say “odd” they mean “odd numbers other than powers of 3.” For example, musicians would not call 9/8 and odd meter, but they would call 7/8 or 11/8 odd.
The most popular piece of music by far written in 5/4 time was Dave Brubeck’s Take Five. It sold over a million records in 1961 and continues to be popular 50 years after it was written. Here’s a video of the Brubeck Quartet performing Take Five in 1966.
[Update: video removed]
And here is a mind-bending mash up of Take Five by Radiohead. (Thanks to @explicitmemory for the link.)
Some music written in odd meters sounds like an intellectual exercise rather than a beautiful tune. The music of Dave Brubeck is a notable exception. In addition to Take Five, he composed other popular music in odd meters, such as Unsquare Dance written in 7/4. (Listen to a sample of Unsquare Dance here.) Another song in 5/4 I enjoy is “How Deep the Father’s Love for Us” recorded by Sarah Sadler.
Update: See the follow-up post on Blue Rondo à la Turk.