In my mind, the definition is a song that has a ballad's pacing and dramaturgy but adds in hard-rock elements like loud guitars and yelled vocals. But yeah, it's murky.
Wiki sez:
FormatTypically, a power ballad begins with a soft keyboard or acoustic guitar introduction. Heavy drums and distorted electric guitars don't enter into the arrangement until the chorus or even later in the song. The electric guitar parts usually take the form of simple root/fifth power chords which sustain until the next chord change, but screaming, melodic guitar solos are also important markers of this genre. The interplay throughout the arrangement between "clean" timbres and distorted ones is crucial to the creation of emotional tension in the power ballad aesthetic.
History Power ballads initially came into popularity at the insistence of a record company in hope of scoring a Top Forty hit, and in the genre's formative years were written only grudgingly by band members. However in recent years, power ballads have been re-imagined as something "authentic" rather than something "manufactured" (i.e. pushed onto bands by record labels)[citation needed]. In any event, power ballads were often a band's most (or only) commercially successful songs. Because of the perceived superficiality of their sentiment, though, power ballads were consistently despised by music critics, who rejected the way metal musicians actively borrowed the musical codes normally reserved for more "authentic" styles of rock.
An important precursor for the form was The Carpenters' "Goodbye to Love" single in 1972, which featured a fuzz-tone screaming guitar solo (by Tony Peluso) situated next to a "middle of the road" vocal.
Power ballads originated in the 1970s with power pop band The Raspberries and arena rock bands like Styx, Boston, REO Speedwagon, Journey, Def Leppard, Queen, and heavy metal pioneers Scorpions. Early examples of power ballads are "Don't Wanna Say Goodbye" from the Raspberries' debut album in 1972, The Raspberries, Styx's "Lady" from their 1973 album Styx II. As a solo artist, Raspberries lead singer and chief songwriter Eric Carmen continued to contribute to the genre by creating the #2 hit "All By Myself" in 1976.
In the 1980s, rock, hard rock and heavy metal bands began to climb the Billboard charts with power ballads, while MTV rotation fueled their popularity. Bonnie Tyler's "Total Eclipse of the Heart" charted in 1983, Scorpions' "Still Loving You" and Night Ranger's "Sister Christian" both charted in 1984, as did Dokken's "Alone Again" in 1985. Prince's "Purple Rain" stands as a prime example of a 1980s power ballad from a genre other than metal.
By the mid 1980s, the rise in popularity of the power ballad was signified with MTV's most requested video for four months straight, "Home Sweet Home" by Mötley Crüe, released in 1985 on the Theatre of Pain album. Many consider it the defining power ballad of the 1980s.
