I thought "PA" always stood for "public announcement"

wiki has an interesting definition..


http://en.wikipedia.org/wiki/Live_PA

Live PA, sometimes written LivePA, meaning Live Personal Appearance or Live Performance Artist is a term used to describe the act of performing, or appearing to perform, electronic music in a concert setting.

While the term "Live PA" literally means "Live Personal Appearance", a legal term originally used to protect promoters when performances are occasionally prerecorded, in common usage it refers to live performance of electronic music, via synthesizers, samplers, and sequencers.

In a performative context, the term was originally used to refer to live appearances, initially at rave events in the late 1980's, of studio based electronic dance music artists. The concept of the Live PA helped provide a public face for a scene that was criticised as faceless by the mainstream music press. The trend was quickly exploited by a music industry desperate to market dance music to a popular audience.