ADVANTAGES AND DISADVANTAGES OF
The most ancient scalloped guitar I have notice of is stored in a museum in Salzburg (Austria) and dates back to the second
half of the 19th century.
Scalloped means that the space between the metal frets on a fretboard have been deepened
to avoid the fingertip touching the wood while playing.
This solution offers a number of advantages and also some disadvantages which affects both the tone and the playing style.
From the 70ies years on, many great players like Richie Blackmore, John McLaughlin, Yngwie Malmsteen has started using scalloped necks to open a third dimension to their tone.
On a scalloped neck fingertips can more easily grip the strings and this highly facilitate some of the guitar playing techniques like bendings, pull offs, tapping, etc. Scalloping also have some impact on the whole guitar tone due to the increased space between the string and the fretboard which enhances volume.
The use of scalloped fretboards may contribute to upgrade your playing speed and technique due to the lighter touch you have to apply on the frets to avoid downward pressure and unpleasant drops in tunings.
You will have to be very light at touch to play on scalloped fretboards, especially in the first positions of the neck toward the nut, where the space between the frets is larger and too much pressure would cause unpleasant drops in tunings introduced due to vertical pressure.
If you're after a scalloped fretboards but your doubtful on applying such an important modification on your instrument, you should consider installing very high types of fretslike for example Dunlop 6000 (the biggest one ever) which playing feel really comes close to a scalloped fretboard.