Today's digital keyboards almost all use some form of synthesis to create their sounds. Whether small, monophonic analog synths to powerful digital workstations with built-in sequencing and recording capability, the contemporary range of synthesizers can be mind boggling. Guitar Center offers many range of synthesizers , and if you are looking for korg synthesizer , you can consult their keyboard department and spend some time discussing your needs and they can help zero in on the one that's right for you . And if you are keen to have a deeper understanding about synthesizers, Guitar Center offers a number of books with great resources for better understanding of synthesis. Synthesizers not only can imitate other instruments but can also make entirely new sounds that could not otherwise exist.
Wild Boar, my hubby, recently owns a second hand electronic keyboard, actually given to him as a gift from his friend with built in sequencing and recording capability and I am sure he will be glad to get some books on synthesis. I have never seen WB so passionate in learning to play the keyboard . Hope the interest will last :)