Underground music comprises a range of different musical genres that operate outside of mainstream culture. Such music can typically share common values, such as the valuing of sincerity and intimacy; an emphasis on freedom of creative expression; an appreciation of artistic creativity. As well, while very few types of underground music are completely hidden—except perhaps the underground rock scenes in the pre-Mikhail Gorbachev Soviet Union—the performances and recordings may be difficult to find for outsiders.
Some underground musical genres never left their non-mainstream roots, such as jagged, aggressive UK 82-style hardcore punk bands like Discharge. Some underground styles eventually became mainstream, commercialized pop styles, such as underground hip hop of the early 1980s, which eventually became popular. In the 2000s, the increasing availability of the Internet and digital music technologies made underground music easier to distribute using streaming audio and podcasts. Some experts in cultural studies now argue that that "there is no underground" because the internet has made what was underground music accessible to everyone at the click of a mouse. One expert, Martin Raymond, of London based company The Future Laboratory commented in an article in The Independent, saying trends in music, art and politics are: ... now transmitted laterally and collaboratively via the internet. You once had a series of gatekeepers in the adoption of a trend: the innovator, the early adopter, the late adopter, the early mainstream, the late mainstream, and finally the conservative. But now it goes straight from the innovator to the mainstream.
In effect, this means a boy band (for instance) could be influenced by a (formerly) obscure 1960s garage rock, early 1980s post punk, noise rock acts like Pussy Galore or even composers of avant-garde classical music like John Cage and Karlheinz Stockhausen and still remain recognisable as a boy band.
A music underground can also refer to the culture of underground music in a city and its accompanying performance venues. The Kitchen is an example of what was an important New York City underground music venue in the 1960s and 1970s. CBGB is another famous New York City underground music venue claiming to be "Home of Underground Rock since 1973".