Synth DIY books
Electronic Music Circuits, Barry Klein
Originally published by Howard Sams, 1982, 302 pages. Now available direct from the author, Electronic Music Circuits in a comb-bound form, updated in 1996.
This is probably one of the better books explaining synthesizer circuits in some detail, covering not only oscillators, filters, envelope generators, voltage-controlled amplifiers etc., but also things like the PSU and keyboard controllers. Though some of the circuits are based around now-obsolete CEM and SSM synthesizer chips, there is much to be learned from this book. It also contains quite a lot of circuits taken from Electronotes, q.v. (And if you intend to get serious about all this stuff and are contemplating buying a copy of this book, getting a copy of the Electronic Music IC Databook at the same time is thoroughly recommended!)
Electronic Music IC Databook, Barry Klein
Published by the author, Barry Klein, along with Electronic Music Circuits (if you are serious about this stuff and are buying that book, buy this one too!).
This is a large (more than 300 pages) compendium of datasheets of old (generally) synthesizer-dedicated ICs. Some of the information is available online, most notably Synthesis Technology's CEM chip page, but for many of the chips, this is likely to be the only place you will find the data.
Chips covered are: CEM: 3310, 3312, 3320, 3328, 3330/3335, 3340/3345, 3350, 3360, 3371, 3372, 3374, 3378/3379, 3387, 3389, 3391, 3394, 3396, PA381/382 (CEM3381/2), PD508, SAM8905. SSM: 2000, 2010, 2011, 2012, 2013, 2014, 2015, 2017, 2018, 2020, 2022, 2024, 2030, 2033, 2038, 2040, 2044, 2045, 2047, 2050, 2055, 2056, 2100, 2110, 2120/22, 2125, 2134, 2200, 2210, 2220, 2300, 2402/12
Electronotes, ed. Bernie Hutchins
Electronotes - Classic synth design.
Musical Applications of Microprocessors, Hal Chamberlin
Hayden, 1985 ISBN 0810457687, 802 pages (2nd edn)
Although primarily concerned with microprocessors and their use within sound and music synthesis, early chapters have introductory material on synthesis in general, including methods using tape, voltage control etc. There is also a nice chapter giving typical examples of basic analogue circuits such as VCOs, VCFs, VCAs etc., with good explanations of how they work.
Op-Amp Cookbook, Walter G. Jung
<add desc> 1st edition good too..
Small Signal Audio Design, Douglas Self