You have a Yamaha PSR-270, which is touch sensitive, MIDI keyboard. Yamaha is a decent make. Have you got touch sensitivity turned on?
Your keyboard is described thus:
"Portable Grand Piano
These keyboards feature Yamaha's exclusive Portable Grand™ function. By pressing the Portable Grand button, the keyboard will exit any other function or mode and set itself up for playing the special stereo-sampled Grand Piano voice..." It then goes on about Superb Sound Quality.
I have owned a lower PSR model than this, and always lusted after a Midi version with touch sensitivity, like yours, for its portability. You will get good money for it on ebay.
The piano Midi Piano samplers are getting better all the time. I use a weighted 88 note keyboard with a computer for sound output via Midi. My Roland digital keyboard would have cost the first owner between 2 and 3 thousand dollars. I paid 300 for it on an auction site. You can tell it is not a cheap DP by the feel, weight. It is well made. It is a better feel than my PSR did. This approach vastly simplifies things. Ignore the sound in shops, you don't need the salesdude to plug it in even. Just go for feel. Korg, Yamaha, Roland, Kawi, perhaps Technics.
DPs are a big let down, especially if you play Scott Joplin, as your ID suggests. They are a bit better with classical stuff.