Btw., I was introduced to Focus by my best friend's big brother when I was a kid. He also taught us about Pink Floyd, Rush and Manfred Mann's Earth Band, lots of great prog rock. But he was always talking about how great Jan Akkerman (the guitarist of Focus) was. He kept sying he was the best guitarist in the world, and in that way Jan Akkerman became my first real introduction to the concept of guitar heros. And Thijs van Leer's falsetto and yodeling opened up my understanding of how the singer could treat his voice like an instrument, not merely as a vehicle for delivering a melody and lyrics. After listening to van Leer, singers started to really inspire me musically.
If you have the time, take a listen to this superb 1973 recording from the Rainbow Theatre (accompanying drugs are optional):