1. By Musical Acoustics we refer to some physics laws which allow us to understand the foundations of Musical Theory. Music which has evolved differently within various Societies (greek and roman, arabo-oriental, hispano-moresque, medieval and then west-european, indian, sino-japanese, etc) is based on the same principles, which explain for instance why the musical scale is composed of seven degrees (5 tones + 2 semi-tones) and why the best way to end up a melody is the chaining dominant seventh chord and tonic perfect chord.
2. After giving some rudiments of Acoustics (sound, vibration, frequency, harmonics, beats), the book explains the building of the musical scale by means of the Circle of Fifths (sketch on cover). This concept has been the platform of all musics throughout the world for 5 millenna. Designed in Mesopotamia, it spread into the antique Persia, then towards the indian sub-continent. Phytagoras brought it in the 6^th century B.C. in Greece whose tetrachord scale had only 4 degrees (the 4 strings of their lyra often seen on ancient paintings).
3. The first turning point in Western Europe occured around 1000 A.D. It was the beginning of Polyphony; De Arezzo achieved the definitive form of music writing, and by the same occasion ruled out the quarter-tone of the greec heritage. At least in theory, since it survived in practice till the Renaissance, but without any theoretical backing, it had been forgotten for a millennium. De Arezzo had nevertheless established a system exploiting the seven ancient modes, in use throughout medieval Europe.
4. A big chapter is dealing with Consonance, the founding-criterion to Just Intonation.This concept has always been misunderstood by music theorists since Boethius around 500 A.D. announced his much debated ideas on this subject. Yet they have influenced scholars during several centuries. The author presents his own vision of just intervals, and points out the failure of simple ratios theory which marked the history of western music.
5. The big Turning Point occured at the Renaissance, due to some theorists who tried to impose scales containing only consonant intervals, very difficult to put into practice.This confusion caused the death of the ancient 7 medieval modes and set the major-minor dichotomy in Western Europe. Only one has been remained in the 16^th century : the major (ionian). The minor (aeolian) will appear in the early 17^th, with a leading note (seventh note raised by half a tone) for harmony-related reasons. This note and its “attraction” towards the tonic can be explained by acoustical arguments. The Russian and the Orthodox Church have kept on using the ancient medieval modes. The Coptic Church of Egypt, in addition to major and minor, has a great variety of modes (non-western, ancient, often with quarter-tones, etc). So, the western music is all but universal, and has strong cultural features.
6. Later on (late 17^th/early 18^th), in order to comply with Just Intonation, some scientists (C. Huygens and J. Sauveur) tried to provide the scale with consonant intervals (such as the harmonic seventh, slightly lower than the minor seventh), this has led them to build temperaments with 31 or 43 degrees. That was the birth of Micro-tonality in Europe, but the first micro-tonal scale in History was designed by Safi Addin in the 13^th century.
7. The micro-tonal attempts have not been pursued since the 12-tone temperament had created a semi-tonal environment which has shaped the hearing, in addition to the difficulty in making convenient keyboards giving more than 12 keys per octave. Micro-tonality will be resumed in early 20^th century in Europe (with Haba, Wyschnegradsky, Fokker) and continued in the USA (with Partch and many others).
8. The most mentioned names are J.-Ph. Rameau and J.-S. Bach (with Pythagoras and Zarlino). Rameau was also a great theorist, he studied the sound nature and the harmonics from a scientific view-point and wrote many treaties which are the basis of modern Harmony. Bach, a keyboard virtuoso, had deeply exploited many tunings or temperaments seeking for chords which best suited his themas. The semi-tones in the 17^th and 18^th temperaments didn’t have the same size, they were not absolutely equal until the middle of the 19^th century.
9. While in Central Europe this led to chromatism (Liszt and Wagner) and then to serialism (Schönberg), in France many composers introduced some non-western tonalities (in their spanish dances), others with quater-tones were discovered by Bartok in his native Hungary. The non-western tonalities will have a real success all along the 20^th century, mainly in USA.
10. The book covers all sides of Musical Acoustics : Scales and Temperaments, Harmonics, Chords, Tonality, Consonance, etc. A great part is devoted to the 20^th century and its Musical Revolution : Atonality, Serialism, Electro-acoustics, Just Intonation. The most significant elements are undoubtedly the comeback of micro-tones and the advent of non-western tonalities.
11. The book is addressed to a large scan of readers, since it needs no background in Physics (neither in Music Theory), every thing is explained (the author has been teaching for more than a quarter of century). In return, the reader has to be very sceptical to dare dismiss many old beliefs deep-rooted in western musical culture, and which have influenced its evolution for a whole millennium. In addition to the Bibliography and its hundred books, a great number of websites are given inside. The author is professor of physics at the University and professor of music at the Conservatoire.

* National Council for Scientific Research

© S. Donval