Does the Guitar is liken by everyone as compared to Sitar. What is the difference?
Theoretically, what you say is possible that some one who plays a guitar could play a sitar and vice versa. However in practice, the playing stance differs and a definite amount of acclimatisation would be needed to understand the differences in the construction of the sound boxes and the fret spacing and hence the resulting notes. While it is common to play chords on a guitar, it is uncommon in a sitar as individual notes are played normally.Moreover, guitars can either be fretless or with frets, whereas sitars always come with frets.
