Classical Khmer music is often divided into three categories: pin peat, the ceremonial music of the former royal courts; phleng kar, the songs of the wedding ceremony; and mahori, secular entertainment music, also originating in the royal courts, that is played by a string-based ensemble. The term mahori is shared with Thai music, and the instrumentation is often identical, although the songs are not.
The music here comes from a cassette originally produced by the Sayonara Music company in the 1980s, and has been dropped from their catalog. As of March 2003, their web site has also been dropped. The performance is from the early 1970s, and features an electric bass and a great deal of reverb. No information is given about the performers; if you know anything about this recording or the performers, please contact me. Mahori songs are usually sung, but these are all instrumentals.
A wonderful site devoted to Cambodian classical dance is here.