Below is a table comparing various temperaments, including Equal Temperament, Pythagorean, another "natural" tuning, two mean-tone tunings, several "Well" temperaments, two "Indian" tunings, two "Persian" tunings. The discussion is carried out using the key of C as example.
By compare, I mean with respect to using - say - a digital tuner to tune a note. Most comparisons of "Well" temperaments benefit more from comparison of intervals (esp. fifths, major and minor thirds), because they are attempting to achieve greatest consonance, normally using Bach's Well Tempered Clavier as a test.
Equal Temperament
divides the octave into 12 equal semitones, each spaced at a ratio of 1.05946 (being the 12th root of an octave, 2). It was propounded by Mersenne in 1636 and came into use in the late 18th century. It is not the same as Well-Temperament, made famous by Bach, despite what some more superficial texts might say.
Pythagorean
builds ratios on the pure perfect fifth (3:2), scaling back into the appropriate octave by dividing by 2, 4 or so on. So D is 9/8, being 3/2 * 3/2, lowered back in to this octave by dividing by 2. Similarly, E is 81/64. However, for a major third, the ear prefers 5/4 (80/64). This difference 81:80 in ratios is called a (syntonic) comma, and is measured at about 22 cents.
A cent is simply a (logarithmic) 1/100th of an equally-tempered semitone, or the 1200th root of two.
Natural
is based on simple ratios and includes the Classic "Just" Diatonic scale. Whereas Pythagorean only allowed 3 as the highest prime, this one allowed up to 17. Variations are achieved by changing the upper limit.
Mean tone 1/4 comma
favoured pure major thirds (5:4), flattening the fifth a bit. This would have worked okay except that it gave rise to ambiguous interpretations for, say, Ab. As G# (two perfect thirds above C), its ratio should be 25:16. As Ab (a perfect third below the higher C) the ratio is 8:5. This led to instrument makers sometimes making keyboards with split black keys for playing each version, or choosing one tuning above the other according to usage, normally C#, Eb, F#, G# and Bb. Others probably became cabinet-makers instead.
Mean tone 1/6 comma
flattens the perfect fifth by sixth of a comma, sharpening the perfect third, but bringing much closer together the enharmonic (black) notes. But you'd still end up with "wolf" notes (intervals that sounded horrible, I guess). This led to ...
Ordinaire
was used in Baroque France for harpsichords and I'm told sounds very nice.
Werckmeister
is a "well" temperament, and achieved 8 pure fifths. The well temperaments would have a different feel for each key, which Bach exploited in his books "The Well Tempered Clavier". It is not known which "well" temperament he intended to be used, though Herbert Anton Kellner believes it to be an adaptation of Werckmeister III, shown below.
Kirnberger
like Werckmeister, is another "well" temperament, and achieved several pure fifths and pure thirds. Kirnberger produced three tunings, called I, II and III.
Young
and Vellotti-Young are yet more Well Temperaments, and the closest to ET that I have seen. Considered very elegant by some, it has lots of perfect fifths.
Persian
tunings for santur (sanduri, santoor, etc.) are included for comparison. They are transcribed from a tonic of E, and flattened by 15 cents so that they can be compared. Their absolute tunings, given in cents from notes derived from A=440, are given here for those people wanting to tune their santurs!
are two Indian musicologists who made great inroads into systematizing Indian music. Their definitions of intervals were expressed as lengths on a string, perhaps in reference to frets on, say, the veena or sitar. It must be noted, however, that both North (Hindustani) and South Indian (Carnatic) musical systems recognise microtonal variations. At least 22 different notes were recognised, each giving rise to different feelings according to their context, but further discussion is beyond the scope of this page!
The table gives the comparison in cents (=100th of an equally tempered semitone). The ratios for Pythagorean and Natural scales are included for comparison.
The enharmonic variations for mean tone tunings are also included.
Note that the Persian tunings have only 8 notes instead of 12.
"C" scale
C
Db
D
Eb
E
F
F#
G
Ab
A
Bb
B
C
Equal temp
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
Pythag
0
114 256/243
204 9/8
294 32/27
408 81/64
498 4/3
612 729/512
702 3/2
816 128/81
906 27/16
996 16/9
1110 243/128
1200 2/1
Natural
0
112 16/15
204 9/8
316 6/5
386 5/4
498 4/3
603 17/12
702 3/2
814 8/5
884 5/3
1018 9/5
1088 15/8
1200 2/1
Mean tone 1/4 comma
0
76 C# 112 Db
193
269 D# 311 Eb
386
504
580
697
773 G# 814 Ab
890
1007
1083
1200
Mean tone 1/6 comma
0
89 C# 108 Db
197
305
394
502
590
698
787 G# 806 Ab
895
1003
1092
1200
Ordinaire
0
77
193
290
386
504
580
696
775
890
997
1083
1200
Werckmeister
III
0
90
192
294
390
498
588
696
792
888
996
1092
1200
Werckmeister
(Kellner)
0
90
195
294
389
498
588
697
792
892
996
1091
1200
Kirnberger
0
91
192
296
387
498
591
696
792
890
996
1092
1200
Kirnberger III
0
90
193
294
386
498
588
697
792
890
996
1088
1200
Young
0
94
196
298
392
500
592
698
796
894
1000
1092
1200
Persian 1
0
130
!!
345
!!
490
630
!!
850
!!
1035
1137
1200
Persian 2
0
125
!!
335
!!
480
625
!!
835
!!
1035
1115
1200
Shrinivas
0
133
204
316
394
498
624
702
835
906
1018
1096
1200
Bhatkhande
0
99
204
316
394
498
597
702
801
906
1018
1096
1200
"Indian" Scale
SA
re
RE
ga
GA
MA
ma
PA
dha
DHA
ni
NI
SA
The only thing they agree on is the octave!
Further reading:
Anthony Baines, The Oxford Companion to Musical Instruments.
Owen Jorgensen Tuning: Containing the Perfection of Eighteenth-Century Temperament, the Lost Art of Nineteenth-Century Temperament, and the Science of Equal Temperament Michigan State University Press, 1991