A good teacher provides the student with guidance.
They also can keep the student from trying too much, or doing too little, and they provide an objective assessment of progress.
I used to specialize in arranger keyboard instruction...it's different from piano and organ, because there was also the importance of teaching the operation of the instrument.
That's how I eventually ended up working as a clinician.
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Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.