Owing to this struggle for life, any variation, however slight and from whatever cause proceeding, if it be in any degree profitable to an individual of any species, in its infinitely complex relationship to other organic beings and to external nature, will tend to the preservation of that individual, and will generally be inherited by its offspring.
––– Charles Darwin

If you look at music, you see theme, variation, you see symmetry, asymmetry, you see structure, and these are related to skills in the real world.
––– Dave van Ronk (American folk singer)

Had St. Jacome written out all the examples for each exercise…this book would be five times its size of 366 pages.
––– Herbert L. Clarke