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mightyscape-1.1-deprecated/extensions/fablabchemnitz/fretruler/fablabchemnitz_fret_scale.py

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Python

#!/usr/bin/env python3
# Distributed under the terms of the GNU Lesser General Public License v3.0
### Author: Neon22 - github 2016
### fret scale calculation code
from math import log, floor
def fret_calc_ratio(length, howmany, ratio):
" given the ratio between notes, calc distance between frets "
# typically 18, 17.817, 17.835 for equal temperment scales
distances = []
prev = 0
for i in range(howmany):
distance = length / ratio
distances.append(prev+distance)
length -= distance
prev += distance
# print "%02d %6.4f %s" %(i, prev, distance)
return distances
def fret_calc_root2(length, howmany, numtones=12):
" using Nroot2 method, calc distance between frets "
distances = []
for i in range(howmany):
# Calculating Fret Spacing for a Single Fret
# d = s-(s/ (2^ (n/12)))
distance = length - (length / (pow(2, (i+1)/(float(numtones))) ))
distances.append(distance)
# print "%02d %6.4f" %(i, distance)
return distances
def fret_calc_scala(length, howmany, scala_notes):
" use ratios from scala file, calc distance between frets "
distances = []
for i in range(howmany):
if i < len(scala_notes):
r = scala_notes[i]
else:
end = pow(scala_notes[-1], int(i / float(len(scala_notes))))
r = end * scala_notes[i%len(scala_notes)]
distance = length - (length / r)
distances.append(distance)
return distances
def cents_to_ratio(cents):
" given a value in cents, calculate the ratio "
return pow(2, cents / 1200.0)
def parse_scala(scala, filename, verbose=True):
""" Parse the readlines() from scala file into:
- description, numnotes,
- lists of pretty ratios, numeric ratios
"""
description = ""
numnotes = 0
notes = []
ratios = []
error = False
# print scala
for line in scala:
try:
# take out leading and trailing spaces - get everything up to first space if exists
line = line.strip() # hold onto this for when we need the description
first = line.split()[0] # first element in the line
# print line
if first and first[0] != "!": # ignore all blank and comment lines
if not description:
# expecting description line first
# may contain unprintable characters - force into unicode
description = unicode(line, errors='ignore')
elif numnotes == 0:
# expecting notes count after description
numnotes = int(first)
else: # expecting sequences of notes
notes.append(first) # for later ref
# remove comments at end of line if exist
if first.count("!") > 0:
first = first[:first.find("!")]
if first.find('.') > -1: # cents
ratios.append(cents_to_ratio(float(first)))
elif first.find("/") > -1: # ratio
num, denom = first.split('/')
ratios.append(int(num)/float(denom))
else:
ratios.append(int(first))
except:
error = "ERROR: Failed to load "+filename
#
if verbose:
print ("Found:", description)
print ("",numnotes, "notes found.")
for n,r in zip(notes,ratios):
print (" %4.4f : %s"%(r, n))
print (" check: indicated=found : %d=%d"%(numnotes,len(notes)))
if error:
return [error, numnotes, notes, ratios]
else:
return [description, numnotes, notes, ratios]
def read_scala(filename, verbose=False):
" read and parse scala file into interval ratios "
try:
inf = open(filename, 'rB')
content = inf.readlines()
inf.close()
flag = verbose
# if filename.find("dyadic") > -1: flag = True
return parse_scala(content, filename, flag)
except:
return ["ERROR: Failed to load "+filename, 2, [1], [1.01]]
### frequency to note
def log_note(freq):
" find the octave the note is in "
octave = (log(freq) - log(261.626)) / log (2) + 4.0
return octave
def freq_to_note(freq):
lnote = log_note(freq)
octave = floor(lnote)
cents = 1200 * (lnote - octave)
notes = ['C','C#','D','D#','E','F','F#','G','G#','A','A#','B']
offset = 50.0
x = 1
if cents < 50:
note = "C"
elif cents >= 1150:
note = "C"
cents -= 1200
octave += 1
else:
for j in range(1,12):
if offset <= cents < (offset + 100):
note = notes[x]
cents -= (j * 100)
break
offset += 100
x += 1
return "%s%d"%(note, int(octave)), "%4.2f"%(cents)
def int_or_float(value):
" true if value is an int or a float "
return type(value) == type(1) or type(value) == type(1.0)
### class to hold info about instrument necks
class Neck(object):
def __init__(self, length, strings=['G','C','E','A'], units='in', spacing=0.4, fret_width=1.5):
" "
# coerce single spacing value into a list of nut/bridge spacing
self.set_spacing(spacing)
# same for fret_width
self.set_width(fret_width)
#
self.length = length
self.strings = strings
self.units = units
self.frets = [] # Treble side frets if fanned
self.bass_frets =[]
self.fanned = False
self.bass_scale = 0
self.fanned_vertical = False
self.method = '12root2'
self.notes_in_scale = False
# Scala
self.scala = False
self.description = False
self.scala_notes = False
self.scala_ratios = False
def __repr__(self):
extra = ""
if len(self.frets)>0:
extra += "%d frets"%(len(self.frets))
if self.method == 'scala':
extra += "(%s)" %(self.scala.split('/')[-1]) # filename
return "<Neck: %s -%4.2f(%s) %s %d strings>"%(self.method, self.length, self.units, extra, len(self.strings))
def set_width(self, fret_width):
" get both values from this "
if int_or_float(fret_width):
fret_width = [fret_width,fret_width]
elif type(fret_width) != type([]):
fret_width = [1,1]
self.nut_width = fret_width[0]
self.bridge_width = fret_width[1]
def set_spacing(self, spacing):
" get both values from this "
if int_or_float(spacing):
spacing = [spacing,spacing]
elif type(spacing) != type([]):
spacing = [1,1]
self.nut_spacing = spacing[0]
self.bridge_spacing = spacing[1]
def set_fanned(self, bass_scale, vertical_fret):
""" keep existing treble calc and create Bass calc
- must have called calc_fret_offsets() before
(so notes_in_scale is set)
"""
# adjust the position of the treble side if required.
# calc fret_offset and if treble or bass side needs to be moved
# if treble - move self.frets
# if bass, add offset as calculated
treble = self.frets
# print treble
if self.method == 'scala':
bass = self.calc_fret_offsets(bass_scale, len(self.frets), method=self.method, scala_filename=self.scala)
else:
bass = self.calc_fret_offsets(bass_scale, len(self.frets), method=self.method, numtones=self.notes_in_scale)
offset = 0 if vertical_fret ==0 else bass[vertical_fret - 1] - treble[vertical_fret - 1]
# print "offset", offset, "bass",bass
if offset > 0:
# shift treble
for i in range(len(treble)):
treble[i] += offset
else: # shift bass
for i in range(len(bass)):
bass[i] -= offset
self.frets = treble
self.bass_frets = bass
self.bass_scale = bass_scale
self.fanned_vertical = vertical_fret
self.fan_offset = offset
self.fanned = True
return offset
def find_mid_point(self, fret_index, width_offset):
""" find midpoint of fret, fret-1 along neck
and ///y width where width_offset=0 means center of neck
"""
y_factor = (width_offset + self.nut_width/2) / float(self.nut_width)
# assume fanned
tpos_f1 = self.frets[fret_index]
bpos_f1 = tpos_f1 if not self.fanned else self.bass_frets[fret_index]
if self.fanned:
if self.fan_offset >= 0:
tpos_f0 = self.fan_offset if fret_index<=1 else self.frets[fret_index-1]
bpos_f0 = 0 if fret_index<=1 else self.bass_frets[fret_index-1]
else:
bpos_f0 = -self.fan_offset if fret_index<=1 else self.bass_frets[fret_index-1]
tpos_f0 = 0 if fret_index<=1 else self.frets[fret_index-1]
else:
tpos_f0 = 0 if fret_index<=1 else self.frets[fret_index-1]
bpos_f0 = 0 if fret_index<=1 else tpos_f0
#
mid_tpos = tpos_f0 + (tpos_f1 - tpos_f0)/2
mid_bpos = bpos_f0 + (bpos_f1 - bpos_f0)/2
# print fret_index, y_factor
# print " %4.2f %4.2f %4.2f"% (tpos_f0, tpos_f1, mid_tpos)
# print " %4.2f %4.2f %4.2f"% (bpos_f0, bpos_f1, mid_bpos)
# the mid_xx positions are self.nut_width apart
return [mid_tpos + (mid_bpos-mid_tpos)*y_factor, width_offset/self.nut_width*1.5]
def calc_fret_offsets(self, length, howmany, method='12root2', numtones=12, scala_filename=False):
" calc fret positions from Nut for all methods "
frets = False # store them in here
if scala_filename:
scala_notes = read_scala(scala_filename)
self.method = 'scala'
self.scala = scala_filename
self.description = scala_notes[0]
self.scala_notes = scala_notes[2]
self.scala_ratios = scala_notes[3] # [-1]
frets = fret_calc_scala(length, howmany, self.scala_ratios)
self.notes_in_scale = len(self.scala_ratios)
elif method.find('root2') > -1:
self.method = method
frets = fret_calc_root2(length, howmany, numtones)
self.notes_in_scale = numtones
elif method == '18':
self.method = method
ratio = 18
frets = fret_calc_ratio(length, howmany, ratio)
self.notes_in_scale = 12
elif method == '17.817':
self.method = method
ratio = 17.81715374510580
frets = fret_calc_ratio(length, howmany, ratio)
self.notes_in_scale = 12
elif method == '17.835':
self.method = method
ratio = 17.835
frets = fret_calc_ratio(length, howmany, ratio)
self.notes_in_scale = 12
# update the iv
self.frets = frets
return frets
def show_frets(self):
" pretty print "
for i,d in enumerate(self.frets):
print ("%2d: %4.4f" %(i+1,d))
if self.bass_frets:
for i,d in enumerate(self.bass_frets):
print ("%2d: %4.4f" %(i+1,d))
def compare_methods(self, howmany, verbose=True):
" show differences in length for the main methods (not scala) "
distances = []
differences = []
methods = ['12root2', '18', '17.817', '17.835']
n = Neck(30) # long one to maximise errors
for method in methods:
distances.append(n.calc_fret_offsets(n.length, howmany, method))
# print distances[-1]
for i in range(1, len(methods)):
differences.append( [a-b for (a,b) in zip(distances[0], distances[i])] )
if verbose:
print("Differences from 12root2")
for i,m in enumerate(methods[1:]):
print ("\nMethod = %s\n " %(m))
for d in differences[i]:
print ("%2.3f " %(d))
print("")
# package
combined = []
for i,m in enumerate(methods[1:]):
combined.append([m, max(differences[i]), differences[i]])
return combined
# Gibson "rule of 18" base scale is in sys 18.
# Martin 24.9 (24.84), 25.4 (act 25.34) rough approx and round up. not actually the scale length
# The difference between 17.817 and 17.835 came from rounding early and carrying the roundoff error through the rest of the work.
# where r = twelfth root of two and put the first fret where it would make the sounding length of the string 1/r of its original length
### tests
if __name__ == "__main__":
n = Neck(24)
f = n.calc_fret_offsets(n.length, 12, '12root2')
n.show_frets()
print (n)
errors = n.compare_methods(22, False)
for m,e,d in errors:
print ("for method '%s': max difference from 12Root2 = %4.3f%s (on highest fret)"%(m,e, n.units))
#
n = Neck(24)
f = n.calc_fret_offsets(n.length, 22, 'scala', scala_filename='scales/diat_chrom.scl')
n.show_frets()
print ("Fanning")
# n.set_fanned(25,0)
# n.show_frets()
# print n
# print n.description
# print n.scala
# print n.scala_notes
# print n.scala_ratios
# similar to scale=10 to scale = 9.94 but slightly diff neaer the nut.
# scala_notes = read_scala("scales/alembert2.scl")#, True)
# print "Notes=",len(scala_notes[-1]), scala_notes[1]
# for d in fret_calc_scala(24, scala_notes[-1]): print d
# test load all scala files
# import os
# probable_dir = "scales/"
# files = os.listdir(probable_dir)
# for f in files:
# fname = probable_dir+f
# # print f
# data = read_scala(fname)
# # print " ",data[0]
# if data[0][:5] == "ERROR":
# print "!!!! ERROR",fname
## freq conversion
print("")
for f in [440,443,456,457, 500,777, 1086]:
print (f, freq_to_note(f))
## fanned frets
# print
# for f in [1,11]:
# print n.find_mid_point(f,-0.75)
# get to this eventually
string_compensation = [
0.0086, 0.0119, 0.0107, 0.0124, 0.0151, 0.0175, 0.020, 0.0222, 0.0244, 0.0263,
0.0282, 0.030, 0.0371, 0.4235
]
### Optionally:
# how many strings,
# (associated sequence of intervals)
### refs:
#http://fretfocus.anastigmatix.net/
#http://windworld.com/features/tools-resources/exmis-fret-placement-calculator/
#http://www.huygens-fokker.org/scala/
# superstart:
# notes on the fretboard
# https://www.youtube.com/watch?v=-jW1Xx0t3ZI