Polyphony skinny and limited opportunities but at this price ...

UTILIZATION

There's no simpler. Screen clutter is sometimes based on what we do, but in general use is intuitive.
The keyboard is a little rubber but it looks solid (it's Yam!)
The ability to plug in a USB stick is nice. The MM6 can read files surprising: I caught him singing a file samplitude VIP live like this! (Well it is a file with a single midi track but still)

SOUNDS

For the price, there is no better. The patches may show more dynamic but must find fault at this price.
Pianos OK
El piano: beautiful
Guitars: excellent and arpeggios are provided for people.
Bass: OK
Organ: diverse and accurate
Synth: not very diverse, some nice pads but it lacks the beautiful webs with slow dynamic developments ...
Percussion: OK
The effects are correct.

OVERALL OPINION

I bought by mail order without trying. I wanted a simple keyboard, no-brainer, with good sound ... The objective is achieved.
The price / quality ratio is exceptional especially since I bought it secondhand for 300 euros.