Well I guess among the general public Focus primarily is known because of the stellar playing of guitarist Jan Akkerman, who could be one of the first rock players who really used a classical influence in his playing. Even now he's regarded as one of the all time greats.
But equally important are the other members of the ever revolving line up of the band, with Flautist/Keyboardist/Vocaliser (that's right, I can't call his yodeling and shouts "Vocals") Thijs Van Leer being the constant.
And then there was the foundation being laid down by Cyril Havermans and later by Bert Ruiter who were perfectly able to play along with the amazing Pierre Van der Linden
‪Focus - House of the King and Focus (vocal)‬‏ - YouTube
"House of the king"
Back then, drummer Pierre Van Der Linden was regarded as being on one par with people like John Bonham and Bill Bruford, this song's tricky timing shows why.
‪Focus - Sylvia‬‏ - YouTube
"Sylvia"
Thijs Van Leer actually wrote this as a vareity song, meant to be sung by a female vocalist, she didn't like the song (Go figure) and so Focus released it on their own, scoring a hit with it. Akkerman's enthusiastic riffing and Van Leer's growling Hammond, no doubt playing important roles too.
‪Focus - Elspeth of Nottingham‬‏ - YouTube
"Elspeth of Nottingham"
A perfect showcase of Akkerman's mastery of the lute.
‪focus - Eruption (1972)‬‏ - YouTube
"Eruption"
Prog at its finest, no matter how you slice it. Note again drummer Piere Van Der Linden.
The last true Focus album was "Hamburger Concerto" after which Akkerman left the band, here's the title track.
‪Focus Hamburger Concerto‬‏ - YouTube
The most notable of the line of guitarists that replaced Akkerman was Belgian player Philip Catherine who added a different vibe to Focus' music.
‪Focus - Live 1976 (w' Philip Catherine): Virtuous Woman*‬‏ - YouTube
"Virtuous Woman"
The footage is out of sinc but the music itself makes up for that.
Focus is still going strong and releasing albums but they go under the radar.
H'mm I get the destinct feeling I forgot something here....
"Hocus Pocus"
‪Focus - Hocus Pocus Live '73‬‏ - YouTube
