David Stewart’s Guide to Specifications!
Q: What’s the difference between weighted action and synth action on keyboards?
A: This refers to the type of mechanical keyboard assembly used. Basically a synth action is a non-weighted set of plastic keys, where a weighted action adds weights to the keys. The difference between how to two feel or play can be substantial. A weighted action will feel a little more like a piano keyboard. Most players would characterize it as slower and with more resistance. A non-player might think this to be a bad thing, but since many players spent some time in their life playing pianos the weighted action is often preferred because it is more like what they are used to.
A synth action, on the other hand, feels more like an organ. The keys are light and capable of being moved very quickly. They also tend to return to their resting position much more quickly. This can be an important advantage when trying to play very fast parts such as lead lines or fast arpeggios. The type of action a particular player prefers is usually determined mostly by what he or she is used to, and secondarily by a particular style or passage of music that may call for one type or another.