The music for the Law and Order shows, is composed by Mike Post whose credits include: Hill Street Blues, The A Team and Magnum PI. The spin-off shows have different variations of the original theme, SVU gained a different arrangement and slightly slower tempo version, whilst up until 2007, Criminal Intent had a jazzy guitar rythum added. From season 7 onwards, the theme was changed to the same tune Mike made for the ill-fated Trial By Jury spin-off.
The composer for the UK broadcasts on Channel Five, is Australian singer, Rob Dougan whose credits include: The Matrix Soundtrack. Until recently Channel Five used an instrumental version of Rob's "There's Only Me", the channel now uses a theme tune penned by Paul Dinletir named "Urban Warfare" for its showing of season 6.
Below is a list of files you can download of the theme tunes, past and present that I have made in .wav format.
The above are music files and upload/download times may be slow depending on your internet connection speed and PC, please be patient.