Music dictionaries are expensive, and they need a lot of space too. But as a musician, conductor, composer or manager of a mandolin club you do regularly need information about composers or musical instruments. 

On this page I have compiled links to some of the important and useful music theory books and dictionaries that I can recommend.

You can read those books or download the complete books from the Internet Archive www.archive.org.

Grove Dictionary of Music and Musicians

The  Grove Dictionary was published in parts from 1878 - 1889. It ist the most important dictionary of music in English until today.

Link collection: https://pinboard.in/u:mandoisland/t:grove/

Search for "grove dictionary" at archive.org: http://archive.org/search.php?query=grove%20dictionary%20AND%20mediatype%3Atexts

I recommend the following editions published in 5 volumes between 1916 and 1920:

Volume 1: http://archive.org/details/grovesdictionary19121grov

Volume 2: http://archive.org/details/grovesdictionary19162grov

Volume 3: http://archive.org/details/grovesdictionary19163grov

Volume 4: http://archive.org/details/grovesdictionary19164grov

Volume 5: http://archive.org/details/grovesdictionary19165grov

Volume 6 (American Supplement 1920): http://archive.org/details/grovesdictionary00grovrich

Riemann Musiklexikon

The Riemann Musiklexikon is the main music dictionary in German. Several editions are  available, including an English edition:

1882 - Musik-Lexikon : Theorie und Geschichte der Musik, die Tonkünstler alter und neuer Zeit mit Angabe ihrer Werke, nebst einer vollständiger Instrumentenkunde (1882): http://archive.org/details/musiklexikontheo00riem

2nd Edition 1884: http://archive.org/details/musiklexikonthe00riemgoog

Riemann Dictionary of Music

Englisch Edition from 1896: http://archive.org/details/cu31924017134168

Englisch Edition from 1908 (Fourth Edition): http://archive.org/details/dictionaryofmusi00riem

Search for "Riemann lexikon" at archive.org: http://archive.org/search.php?query=riemann%20lexikon%20AND%20mediatype%3Atexts

Baker's biographical dictionary of musicians (1919)

1919: http://archive.org/details/bakersbiographi00bake

1940: http://archive.org/details/biographicaldict00bake

W. S. B. Mathews und Emil Liebling - Pronouncing and defining dictionary of music

1876: http://archive.org/details/pronouncingandd00liebgoog

Curt Sachs - Real-Lexikon der Musikinstrumente, zugleich ein Polyglossar fuer das gesamte Instrumentengebiet (1913)

Dictionary of musical instruments

Emil Teuchert - Musik-Instrumentenkunde in Wort und Bild : zusammengestellt (1910)

Musical instruments in text and pictures

Hermann Ruth-Sommer, Alte Musikinstrumente: ein Leitfaden für Sammler (1916)

Old musical instruments - A guide for collectors

Mary E. Brown  und  William Adams Brown  - Musical instruments and their homes (1888)

A great book with beautiful drawings of musical instruments:

Carl Engel

Carl Engel was a musicologist and collector of musical instruments. His collection became the base of the musical instruments collection of the Victoria and Albert museum in London.

His books contain many great pictures and woodcuts of musical instruments:

A descriptive catalogue of the musical instruments in the South Kensington museum, preceded by an essay on the history of musical instruments (1874):

http://archive.org/details/descriptivecatal00vict

Musical instruments (1875):

http://archive.org/details/musicalinstrumen00engeiala

The music of the most ancient nations : particularly of the Assyrians, Egyptians, and Hebrews : with special reference to recent discoveries in western Asia and in Egypt (1864)

Researches into the early history of the violin family (1883)

http://archive.org/details/researchesintoea00enge

Alfred James Hipkins: Musical instruments : historic, rare and unique (1921)

Illustrated by a series of fourty-eight plates in colours drawn by William Gibb

Great book with color plates, including many plucked instruments!

H. W. Schwartz - The Story Of Musical Instruments (1938)

August Reissmann - Illustrierte Geschichte der deutschen Musik (1881)

Illustrated history of music in Germany (1881)

http://archive.org/details/illustrirtegesc00reisgoog

Allgemeine Geschichte der Musik : mit Bildern und Notenbeispielen (1909)

General history of music with pictures and musical examples:

Hermann Ritter - Allgemeine illustrierte Encyclopädie der Musikgeschichte in 6 Bänden:

Illustraded encyclopaedia of music history in 6 volumes:

Hans Merian, Berhard Egg - Illustrierte Geschichte der Musik von der Renaissance bis auf die Gegenwart (1913)

http://archive.org/details/illustrierteges00egggoog

Ludwig Bussler

Musikalische Formenlehre in dreiunddreissig Aufgaben, mit zahlreichen, ausschliesslich in den Text gedruckten Muster-Uebungs- und Erläuterungs-Beispielen, sowie Anführungen aus den Meisterwerken der Tonkunst .. (1878)

http://archive.org/details/musikalischefor00bussgoog

http://archive.org/details/musikalischeform00buss

All works by Ludwig Bussler at archive.org:

http://archive.org/search.php?query=creator%3A%22Ludwig+Bussler%22

Wohlfahrt, Heinrich (1797-1883)

Wegweiser zum Componiren für Musik-Dilettanten welche sich in kurzer Zeit und ohne Hülfe eines Lehrers befähigen wollen, Melodieen zu bilden und mit passender Begleitung zu versehen, ...

Guide to musical composition in the invention of melodies : their transformation, development and suitable accompaniment (1859)

Marx, Adolf Bernhard, 1795-1866

Die Lehre von der musikalischen Komposition : praktisch-theoretisch (1887)

Search for "marx composition" at archive.org: http://archive.org/search.php?query=marx%20komposition

Teil 1: http://archive.org/details/dielehrevonderm05marxgoog

Teil 2: http://archive.org/details/dielehrevonderm02marxgoog

Teil 3: http://archive.org/details/dielehrevonderm03marxgoog

Teil 4: http://archive.org/details/dielehrevondermu04marx

Teil 4: http://archive.org/details/dielehrevonderm04marxgoog

Theory and practice of musical composition (1854)

More books about composition, musical form etc.:

Search for "composition music":

Search for  "musikalische Formenlehre"

or

http://archive.org/search.php?query=subject%3A%22Musical+form%22