The sound quality is nice, almost like real-world, Casio claims in CTK-631's manual that the sound samples were taken from 3 different frequencies for each on the tones, and then they were digitally stored. If you can adjust the built-in synthesizer, you can expect to hear sounds equal to KORG Trinity.

The blue backlit large LCD gives you more information then you will ever need. At nite time, you can turn off your room's light and believe me the light from the backlit LCD lightens your room magically.

It works with MIDI as if it was made for MIDI, plug the cable, and try listening to the midi files from the internet, you'll be amazed!, because then it would be using all its 16 tracks in real time, sounding so real as if the band is sitting next to you room playing. rhythms are ok, but lacks real time channel mute function (normal in Yamaha's PSRs) althou you can mute individual track by using its built-in mixer, but it takes time and you cannot do it while you are playing a song.(the song will stop) There are 10 out of 100 rhythms which are very usable, rests are some sort of childish and sounds very similar to each others. I do agree that for rhythm part, Casio still lags behind somehow compared to Yamaha.

You can create your own tones and store them, upto 32 tones. But dont be surprised if you unplug the unit, all the user data is lost! but then same story with Yamaha!

Let me remind you once more that this unit is outstanding considering the features it offers at such a low price. Synth+16track mixer+Sequencer+TouchSenitive+GM MIDI etc. Only drawback is rather shallow rhythms, and polyphony (# of sounds u can play at once)limited to 24, while most of Yamaha's are 32 note polyphony.

---Kam