IMO the single Finger chord thing from Yamaha is weird.
Destroying playing skills
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The SX600 has a smart chord feature what enables you to play songs with one - finger too, like also in the standard fingering chords modes.
Yamaha is thinking on people who want quick play songs with sophisticated chords what really user friendly is.
Playing with one-finger is not a big deal compared with playing full chords
Everyone can play on his own way he or she likes the most and with a single chord you can concentrate on the melody
Pop
F major C7 C#dim Dm7 Eb C/E Fadd9 F#dim7 Gm7 Abdim7 Am7 BbM7 Bdim : all with one finger in a particular key