I recently received my new Castillo fanned fret 9 string.
F#1 at 72 centimeters, B1, E2, A2, D3, G3, B3, E4, A4 at 60 centimeters. Perpendicular fret at #3, making for much more comfort than a higher perpendicular fret. Carpathian spruce and cocobolo. The cocobolo's density makes the basses very solid. Lattice brace design transfers the severely-angled-bridge force to the top in a very different way than fan bracing which is optimized for a straight traditional bridge.
This is a fabulous, fully successful guitar, based on info gained from a prototype I had built in 2013, which was not so successful.
pics on the other thread soon (search Brahms Guitar Specs)
Some people here are unaware that the numbered octaves go from C to C, thus, B1 is the highest note in the first octave with C2 being a half step above.
My F#1 is a whole step above the lowest string of a four-string contrabass. From here down, the next register would be at C#1, and the next at G#0. (I have no plan to use those deeper registers ever. I consider the F#1 to be the lowest pitch necessary for my purposes. Note that it is a half step lower than the deepest baroque lute.)
The question has been whether such a bass range is attainable with a classical guitar with a normal sized body. Yes it is, but obviously only with a very high quality build and some attention to the internal design. My F#1 is a great success, but friendly critics have already asked whether it would not have been even better at 74c. Yes, it would. However, a length of 72c was barely imaginable to me in terms of playability in planning the design. Actually this is not really an issue though there are others. A peripheral lesson is that very long low basses are perfectly functional in a fanned fret design, and the makers of Brahms Guitars would do very well to extend the low B1 out toward 70 centimeters for the low B in order to eliminate the tubbiness and poor intonation.
Piano music: the problem with piano music is not lack of range but lack of fingers. The pianist can achieve 10 notes at once and can play two florid contrapuntal voices with each hand. The guitarist is challenged to play once florid voice alone. Even with my very radical extended range design, it would REQUIRE FOUR HANDS to play any of the major keyboard repertory. It is very possible to _study_ such keyboard music - I have read all of the Bach Inventions and Sinfonia and a good part of the WTC - but performing it is probably not possible. On the other hand, the easy two-part keyboard pieces in the Anna Magdalena Bach notebook are quite possible, but a lot of work. The 3-part pieces in the AMB notebook are interesting to study but the keyboard voicings even in these easy keyboard pieces are simply too un-idiomatic for the guitar in any conceivable tuning, I believe. Don't think that there is some magical new design configuration that will make keyboard music work on a guitar. On the other hand there is room for a new original repertory, which I am busy creating for myself, but nobody else will be able to play it. Ha!
A "guitar" with a high A4 string is a very different-sounding instrument. (You may imagine Segovia's comments.) The sound will always be somewhat more "lutelike" and will perhaps lack that certain earthiness and sensuality of the spanish guitar.
Although Fred Fernseher had a luthier build him a 10-string fanned fret 54c - 68c tuned E1 A1 D2 G2 C3 F3 A3 D4 G4 C4, based on my own experience with the 2013 prototype, this design probably wouldn't perform well for my purposes. The low E1 would be too short and tubby and probably make clicking sounds on the frets, and the high C4 would lack body, but obviously I never played the thing to find out. There is a youtube video.
Low bass strings are available from Savarez, D'Addario, La Bella, and Aquila, to name some off the top of my head. My low F# is a .075" diameter, which turns out to be perhaps a little thin, and I will shortly order whatever sizes are available up to .080" diameter for trial. For my high A4 I am currently using a .022" D'Addario rectified nylon. On a guitar with a radical fanned fret design all of the strings must be calculated and purchased individually because, of a normal six-string packaged set, only one string will be at its correct tension and all the others too loose or too tight.
My reason for choosing a fanned fret design is that I want all of the strings to be equal in function. When I want to play bass, I want to use conventional fingering patterns. The low basses of the various harp guitars, alto guitars, Yepes-style 10 strings, etc. are all pretty worthless from this point of view for various reasons. The diatonic tuning pattern means a great deal of un-necessary redundancy, and carries the problem of damping the unwanted continuing tones and sympathetic vibrations. The extended neck of the alto guitar prevents effective use of the low chromatic notes. On the Yepes-style or the Marlow-style 10 string at 65 centimeters, the low strings are far too thick to sound well when fretted.
Yes, the 80mm wide neck is too wide to play many otherwise potentially juicy chords. Again, four hands would be nice. But having access to 5 octaves using conventional techniques (i.e., no different set of techniques for a bunch of open bass strings) is a very intoxicating experience. Anything with six strings looks like a toy now.