N E W 5 - O C T A V E H A R P S I C H O R D S I N
T H E N E A P O L I T A N S T Y L E
The string-scaling design and soundboard layout
Acoustically in order to sound their best strings need to be stretched to a point where they are almost at their breaking point (they are then said to be critically stressed). At a pitch of about A415, yellow brass strings which are based on a c2 length in the range of about 273 to 295mm are close to breaking. This is in the range of about c2 = 12½ to 13½ once. Here, because of the (basically) F1 to f3 compass the instrument is to be designed basing the scalings on the lengths of the f strings rather than on the c strings. Therefore the length of f1, a perfect fifth lower with strings that are 50% longer should be in the range 1.5x12½ = 18¾ once to 1.5x13½ = 20¼ once in length. For simplicity the treble scalings were designed on an f1 scaling of 19 once. This would mean that the length of the note C# would be about 2200mm, which is a length that is unrealistically long. Hence the scalings were designed so that C# was 90 once (= 1965mm) in length with strings that were Pythagorean from the top note down to the note c, and then gradually foreshortened from c down to the note C#.
Similarly the red-brass scalings were chosen to give red-brass strings that were critically stressed with a c2 length of about 210 to 230mm or about 9½ to 10½ once. Again for simplicity the scalings for hard red bass stringing were based on a c2 length of 9 2/3 once (or f1 = 14½ once), and the slack scalings for soft red-brass were based, again for simplicity, on f1 = 11¾ once.
This gives the following string lengths:
g#3 = 4 once
f3 = 4¾ once
f2 = 9½ once
f1 =19 once
f = 38 once
F = 73 once
C# = 90 once
C = 77½ once
A1 = 92 once
G#1 = 79 once
F1 = 94 once
The notes in yellow were strung in yellow-brass strings, those in red in hard red-brass strings and those in violet in soft red-brass strings. Click on the image below to see these scalings plotted as a logarithmic graph:
Click on this image so see a logarithmic plot of the string scalings
The plucking points of the rear register plucking the long string were based on those found on a number of Neapolitan instruments, particularly those of Onofrio Guarracino, and were chosen to be 2 once for f3, 6 once for f, and 8 once for F1.
