I saw this yesterday at the Seattle International Film Festival and recommend it highly:

It's recent Cambodian history—from independence in 1953, to constitutional monarchy under King Norodom Sihanouk, to the 1970 coup by Gen. Lon Nol, to the bloody takeover by the Khmer Rouge in 1975—as seen through popular music. The history is tragic, the music energetic. Interestingly, Cambodia was initially more influenced by European rock and roll stars such as Johnny Hallyday and Cliff Richard rather than the American progenitors: Elvis, Chuck Berry, Buddy Holly. U.S. rock became more prevalent once U.S. armed forces arrived in South Vietnam and the radio began playing Wilson Pickett and James Brown.  

A key line in the doc (and in the trailer: 2:05) is about life under the Khmer Rouge:

If you want to eliminate values from past societies, you have to elminate the artists. 

It's a line that resonates beyond its tragic meaning in Cambodia. You wonder, in fact, if we‘ve done something similar in the U.S. but via the free market. What’s popular now isn't generally artistic and what's artistic isn't generally popular.

Wednesday's showing was its last at SIFF but look for it in the usual places. Saturday, for those interested, I‘ll be seeing a documentary on Cambodia’s Dr. Haing S. Noir who won an Academy Award in “The Killing Fields” and who was murdered under mysterious circumstances in 1996.