I look for unevenness, for letters that are over- or under-weight, for any inconsistencies that might flag the flavour. Every letter must be independently legible so that if it is seen out of context it will not be misread. Finally the entire alphabet must be ‘in tune’…. The oboe is the first instrument you hear when a symphony orchestra begins to ‘tune up.’ The oboe gives the pitch. It has great penetration and can easily be heard by all the other instruments. Now comes a surprising coincidence: the letters O B E in the word OBOE and the lowercase letters o b e—or preferably o d e—are, by the nature of their design, key letters that give the pitch to which other letters of the alphabet may be tuned. O B E and o d e carry a big load in determining the character of a style. They are not dramatic shapes like a or g or s, but they sound the pitch clearly. First they must be in tune with each other, then the remaining letters should be in design harmony or in artistic balance with these three. All must be in tune.”
Edward Rondthaler, Life with Letters, as they turned photogenic, 1981.