Music historian Bill Martin says that the release of "Rubber Soul" was a "turning point" for pop music, in that for the first time "the "album" rather than the song became the basic unit of artistic production." In author David Howard's description, "pop's stakes had been raised into the stratosphere" by "Rubber Soul", resulting in a shift in focus from singles to creating albums without the usual filler tracks. The release marked the start of a period when other artists, in an attempt to emulate the Beatles' achievement, sought to create albums as works of artistic merit and with increasingly novel sounds. According to Steve Turner, by galvanising the Beatles' most ambitious rivals in Britain and America, "Rubber Soul" launched "the pop equivalent of an arms race".