Screamo (combination of two words: scream and emo) is an aggressive subgenre of emo that emerged in the early 1990s. The genre is characterized by tortured screaming vocals and fast, harmonized guitars.
Lyrics in screamo are mostly personal in nature. Most of screamo songs use imagery and metaphors to describe personal attitude toward various problems.
It was pioneered by San Diego bands Heroin and Antioch Arrow and developed in the late 1990s mainly by bands from the East Coast of the United States such as Funeral Diner, Saetia.
Gern Blandsten Records and Troubleman Records released many very influential records of the time and region. Many of bands were involved in the ABC No Rio club scene in NYC, which was a self-reponse to the brutality and stagnation of the scene with bands playing at CBGB, the only small place of active hardcore in NYC at the time.
There was an "explosion" of bands, some of the bands that provoked it were Indian Summer, Evergreen, Shotmaker. Eventually these bands began to play what is called emo, a style that reinforced the dramatic aspects of vocal performance in order to achieve the greatest unity with the audience. Their musical origins differ Evergreen produced some of the richest emo sounds, while Shotmaker moved away from hardcore punk and found their place in the brutal frankness of the human voice. The result was a powerful emotional outburst that often left emo bands and their audiences either crying, screaming, or very quiet after performances.
At present, screamo is experiencing a new wave of popularity (so-called screamo-rivival) and for example you can listen to Orchid.