CCR gained moderate success with their 1968 debut album 'Creedence Clearwater Revival', however; it was 1969 that things would really take off led by John Fogerty (guitarist,singer,songwriter,producer).
I would have to say the most musically influential and commercially successful bands of the late 60s and early 70s was Creedence Clearwater Revival with a mix of rock and the essence of country, R&B and blues.
Some bands nail an identifiable group sound the first time out in the studio, i.e. The Doors and Traffic, however; some don't and I'll give you some examples.
Johns worked with the newly formed Led Zeppelin on their debut album of 1969, 'Led Zeppelin', Johns knew without a doubt that a dynamic new sound had been born.
Grateful Dead guitarist and singer Bob Weir wrote some memorable songs with Robert Hunter, however; his primary collaborator was lyricist John Perry Barlow.