Underground music may tend to express common ideas, such as high regard for sincerity and intimacy, freedom of creative expression as opposed to the highly formulaic composition of commercial music, and appreciation of artistic individuality as opposed to conformity to current mainstream trends. Apart from perhaps the underground rock scenes in the pre-Mikhail Gorbachev Soviet Union, or the modern anti-Islamic metal scene of theocratic states in the Arabian Peninsula, very few types of underground music are completely hidden, although performances and recordings may be difficult for outsiders to find.
Some underground rock bands never got non-mainstream roots. They are radical, aggressive 60s bands such as The Velvet Underground, The Stooges, MC5, 70s bands like The Sex Pistols, The Damned, The Clash, and 80s hardcore punk bands like Discharge. Some underground styles eventually became mainstream, commercialized pop styles, as did for example, the underground hip hop style of the early 1980s. In the 2000s, the increasing availability of the Internet and digital music technologies has made underground music easier to distribute using streaming audio and podcasts. Some experts in cultural studies now argue 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 such as John Cage and Karlheinz Stockhausen, while maintaining recognizability as a boy band.
The term "underground music" has been applied to various artistic movements, for instance the psychedelic music movement of the mid-1960s, but the term has in more recent decades come to be defined by any musicians who tend to avoid the trappings of the mainstream commercial music industry otherwise it tells only truth through the music. Frank Zappa attempted to define "underground" by noting that the "mainstream comes to you, but you have to go to the underground." In the 1960s, the term "underground" was associated with the hippie counterculture of young people who had dropped out of college and their middle class life to live in an off-the-grid commune of free love and cannabis. In modern popular music, the term "underground" refers to performers or bands ranging from artists that do DIY guerrilla concerts and self-recorded shows to those that are signed to small independent labels. In some musical styles, the term "underground" is used to assert that the content of the music is illegal or controversial, as in the case of early 1990s death metal bands in the US such as Cannibal Corpse for their gory cover art and lyrical themes. Black metal is also an underground form of music and its Norwegian scene are notorious for their association with church burnings, the occult, murders and their Anti-Christian views. All of extreme metal is considered underground music for its extreme nature.
Shlomo Sher's "philosophy for artists" argues that there are three common misconceptions about the "underground": that it refers exclusively to the rave/electronica scene; that it can be described with a vague, broad definition of "anything which is not mainstream"; and the myth that underground music is kept secret; he points out that no band or performer "exclud virtually anyone or anything" using "secret passwords and hidden map points". Instead, Sher claims that "underground music" is linked by shared values, such as a valuing of grassroots "reality" over music with "pre-wrapped marketing glossing it up"; sincerity and intimacy; freedom of creative expression is valued over commercial success; art is appreciated as deeply meaningful fashion; and the Underground "difficult to find", because the scene hides itself from "less committed visitors" who would trivialize the music and culture.
In a Counterpunch magazine article, Twiin argues that "Underground music is free media", because by working "independently, you can say anything in your music" and be free of corporate censorship. The genre of post-punk is often considered a "catchall category for underground, indie, or lo-fi guitar rock" bands which "initially avoided major record labels in the pursuit of artistic freedom, and out of an 'us against them' stance towards the corporate rock world", spreading "west over college station airwaves, small clubs, fanzines, and independent record stores." Underground music of this type is often promoted through word-of-mouth or by community radio DJs. In the early underground scenes, such as the Grateful Dead jam band fan scenes or the 1970s punk scenes, crude home-made tapes were traded (in the case of Deadheads) or sold from the stage or from the trunk of a car (in the punk scene). In the 2000s, underground music became easier to distribute, using streaming audio and podcasts.