The UK classical chart is a commercial monitoring and marketing device used by the UK music industry to measure its effectiveness in promoting and selling CDs, nominally in the field of classical music. The measurements are made by collating the returns of sales from a number of well known music stores on a regular basis, and this enables a ranking to be established. However, many of the CDs sold are in fact either compilation CDs, or crossover CDs, and are not considered to be classical music by serious musicians.