Hi Ramki,
here I found a definition of the different voice types from a Tyros2 which I think is also valid for the PSR-S650:
Voice Characteristics
The Voice type and its defining characteristics are indicated above the Preset voice or Custom voice name.
Live! These acoustic instrument sounds were sampled in stereo, to produce a truly authentic, rich sound—full of atmosphere and ambience.
Cool! These Voices capture the dynamic textures and subtle nuances of electric instruments—thanks to a huge amount of memory and some very sophisticated programming.
Sweet! These acoustic instrument sounds also benefit from Yamaha’s sophisticated technology—and feature a sound so finely detailed and natural, you’ll swear you’re playing the real thing!
Drums Various drum and percussion sounds are assigned to individual keys, letting you play the sounds from the keyboard.
SFX Various special effect sounds are assigned to individual keys, letting you play the sounds from the keyboard.
Organ Flutes! This authentic organ Voice lets you use the Voice Set to adjust the various footages and craft your own original organ sounds.
MegaVoice
The MegaVoices are not intended to be played from the keyboard but are designed to be used with recorded MIDI data (including songs and styles). MegaVoices make special use of velocity switching, with completely different sounds in the various velocity ranges. For example, a guitar MegaVoice has a huge variety of specific performance techniques assigned to different velocity ranges—making the voice difficult to “play” in real time (because of the precise velocities needed), but very useful when creating realistic tracks with MIDI data, especially when you want to
avoid using several different voices just to make a single instrumental part. Sound maps for the Tyros2’s Megavoices are given in the separate Data List booklet.
S. Articulation!
The Super Articulation voices sound remarkably authentic and natural, featuring the unique performance characteristics of each instrument—for example, guitar scratching sounds or the legato phrasing of wind instruments. They provide many of the same benefits as the MegaVoices, but with greater playability and expressive control in real time. To effectively play these natural sounds in performance of certain voices, you may need to use the pitch bend wheel or footswitch. For details on how to best play each voice, call up the Information window (pressing the upper [6] button in the voice’s Open/Save display).
Live!Drums These are high-quality drum sounds taking full advantage of Stereo Sampling and Dynamic Sampling.
Live!SFX
These are high-quality Latin percussion sounds taking full advantage of Stereo Sampling and Dynamic sampling. They give you a broader and more versatile range of Latin percussion than the normal drum Voices.
Custom! Custom voices which you have created by using the Custom voice function.
CustomWA! Custom voices which contain Wave data.