"The student who wishes to acquire a firm technique on the guitar should not neglect the patient study of scales. If he practices them two hours a day, he will correct faulty hand position, gradually increase the strength of the fingers, and prepare the joints for later speed studies. Thanks to the independence and elasticity which the fingers develop through the study of scales, the student will soon acquire a quality which is very difficult to gain later: physical beauty of sound. I say physical, because sonority and its infinite shadings are not the result of stubborn willpower but spring from the innate excellence of the spirit. In order to derive the greatest possible benefit from the following exercises, play them slowly and vigorously at first, more lightly and rapidly later. Many hours of arduous and frequently futile exercises can be condensed into one hour of scales. The practice of scales enables one to solve a greater number of technical problems in a shorter time than any other exercise."

- Andrés Segovia

http://www.classtab.org/segovia_scales.txt