Mark 2 - David Gilmour (Vocal and Guitar), Nick Mason (Drums), Roger Waters (Vocal and Bass) and Rick Wright (Keyboards).
Pink Floyd was one of the most important groups in musical history. After the former singer, guitarist and songwriter genius Syd Barrett was out, Pink Floyd eventually changed their styles from Psychedelic, Space Rock soon into Progressive Rock.
After the experimental Ummagumma (1969) and Atom Heart Mother (1970), Meddle (1971) was the first Prog record of Pink Floyd. That included the epic Echoes, my favourite Pink Floyd's song; the 23mins piece filled the whole second side of LP.
And then the Dark Side of the Moon was released in 1973, which now is one of the all time classic rock records. Songs inside were linked and some tape effects, samples were used to provide a psychedelic trip for listener; the lyrics were about the pressure, the loneliness and the alienation in modern life. Musically, the success of the album was because Pink Floyd found a balanced point for abstract noise and their soft Jazz-based sound.
After the album, Roger Waters was widely accepted as a good lyricist and songwriter. And of cause Pink Floyd became a great band that took the attention from the whole world. So for the following album, they worked really under pressure, though Wish You Were Here (1975) was another great record.
The Wall (1979) took Pink Floyd to the second and the last high peak of their creative life; it's a 4LPs concept album about the life of Pink. This fictional character who father died in war, had a fearful childhood, then becoming a rich and famous Rock star but depressed and, almost neurotic. It was the last message from the anti war generation.
Released in a time that progressive rock diminished and the Punk movement. The sound of Pink Floyd was changed, no more psychedelic but intense, energetic and powerful sound.
The Wall was filmed in 1982 by Alan Parker; the whole album was bought to the big screen, to make the album and Pink Floyd became the legend.
The Wall Live 1980
In fact, The Wall was like the solo work of Roger Waters, 99% materials inside were written by him. That didn't mean the rest of the members did nothing but just Waters took control of the band. After releasing the last album, the Final Cut in 1983, Pink Floyd was officially disbanded.
For few years spending in court, the rest of the members, David Gilmour, Nick Mason and Rick Wright could keep using the name of Pink Floyd. This line up released 2 studio albums, A Momentary Lapse of Reason (1987) and The Division Bell (1994), but they never sounded good as their old period anymore.
Between other Prog Rock groups, Pink Floyd was different, their sound was darker, and Roger's lyrics always bare and got its depth. Actually, before turning into a psychedelic/Prog Rock band, Pink Floyd was more like a Jazz group (The name Pink Floyd is based on the Jazz/Blues musicians, Pink Anderson and Floyd Council). It could be seen in their rhythm section, Nick Mason and Roger Waters. And Richard Wright is a more Jazz influenced keyboard player rather than Classical influenced (His first solo album, Wet Dream.). Finally, David Gilmour's guitar playing is between Blues and psychedelic. (Technically based on Blues, but the sound and effect he used made it psychedelic). Beside, they used lots of saxophones, plus the use of tape effects; all these became the trademark of unique Pink Floyd sound.
In live performance, Pink Floyd always provided amazing visual elements: like they were the very first group to use light effects. And at the later The Wall tour, they played under a great wall which keep building, while David was playing guitar 20 ft. far from Roger, just before the concert ends, the built great wall would be broken down and collapsed, as follow the music contents.
They influenced not merely seen on guitar-based group but even in ambient, industrial and trip hop, mostly because the music of Pink Floyd was atmospheric. For nowadays band, Radiohead is the group that greatly influenced by Pink Floyd, just from the album, OK Computer to the latest Amnesiac, their arrangement, sound chosen all make you think of old Pink Floyd.
I believe Pink Floyd is the second most influential group in the music history, just beneath the Beatles.