Copyright on sound recordings in Britain generally expires 50 years after they are released or, if unreleased, after they are made. They then enter the public domain and are up for grabs. (In the US, copyright varies from state to state.)
From the point of view of composers and performers who are still alive, and in some cases heirs to artists' estates, this is a slightly raw deal. However, it does mean that after the half century has elapsed, a lot of music can be made available at a reduced price.
It also means that in Britain compilers of albums have a freer hand in selecting material, and a plethora of samplers of varying quality covering some of jazz's greatest vintage years have accordingly been assembled by companies such as Proper Records, JSP Records, Charly Records and Chrome Dreams.
In Hong Kong, the same copyright law stipulations apply, and provided the foundation for the Naxos jazz catalogue.
Thanks to that 50-year rule, compilers are now able to use recordings from the early 1960s; one good new release of this kind, on Chrome Dreams, is Playing It Cool: Classic West Coast Jazz 1953-1961.
The terms "cool jazz" and "west coast jazz" are often conflated, although the landmark Miles Davis 78s from 1949 and 1950, later collected and re-released as The Birth of the Cool, were recorded in New York. Regardless of that title, the real birthplace of "The Cool" is arguably not on either coast of the US but in the Midwest.
The first identifiable progenitors of cool jazz were cornetist, pianist and composer Bix Beiderbecke, and saxophonist Frank Trumbauer, from Iowa and Illinois respectively, who played together in St Louis.