This is first of several very unusual instruments commissioned from me by multi-instrumentalist and solo-performance artist Todd Green. Todd and I refer to it as "the double-neck classical", which gives a good impression of what the instrument is. However, "double-neck nylon string" would be a better name since "classical guitar" is used to denote a very specific type of instrument which, by virtue of having two necks, this instrument most certainly is not. I'll refer to it simply as "the double-neck".
The main neck is indeed set up like a fairly typical classical guitar in scale length (660mm) and fretboard width (55mm at nut), with six nylon strings that can be tuned in a variety of ways including standard guitar tuning. The second neck, set on the bass side of the main neck with plenty of playing space in between, is a 34-inch scale six-string, nylon-string bass. It could be tuned a full octave below the main neck in standard tuning, though Todd employs a variety of alternate tunings on the instrument. The double-neck was designed to have both necks be fully playable, with the body shape and size such that in playing position the main neck would not feel too dissimilar to the Ramirez classical that Todd had been used to playing. The instrument went through a couple of iterations, including removal and re-bracing of the top (see construction page) before we got something that satisfied Todd's needs.
The double-neck has a top of western red cedar, gorgeous back and sides of a wood that was sold to us as Brazilian rosewood and may or may not be that, necks of Mexican cedro, fretboards of ebony and a bridge of cherry. Although we initially had an internal pick-up system in the instrument, it proved unsatisfactory and was removed in favor of a purely acoustic sound.
The nylon-string bass is rich, warm and sweet; the main strings are quite strong and bright. It took a lot of work to get a pleasing response and balance from both necks but ultimately we succeeded. The double-neck has become one of Todd's main instruments in performance and recording, and he composes music to make wonderful use of its extended range and unique sound.
For more about Todd Green's music, available recordings and his amazing collection of instruments, check out his great website, toddgreen.com.