Synth Secrets (1999–2004)
soundonsound.com
soundonsound.com
Or read the books by Brian Shepherd (Refining Sound) or Rick Snoman (Dance music manual). For somebody serious, there's books by Miller Puckette and Charles Dodge
There are plenty of good online tutorials too.
This is quite a dated series now, and I always found it slightly self-indulgent even when it was fresh. Some of the theory is still useful, but digital synthesis has moved on. You can do a lot more with digital code-based systems, or even modern VSTs, than you can with vintage synths from the 1970s.
Pretty much everyone uses samples when they need the sound of a real instrument or a classic drum machine, and this series doesn't spend nearly enough time on the art of abstract electronic sound design or (say) using the FFT features in Max/PD/some VSTs.
What a shame this was produced for a paper magazine rather than directly for the web. It would make a huge difference to be able to listen to the progression within an article, rather than having to imagine it from waveform screenshots.
One important point about them is they emphasize creating familiar instruments such as guitar, flute, etc.
That is a bit different - and rarer and more valuabe! - than most synth tutorials that teach ADSRs, VCFs, etc.
Also, to contextualize them a bit, they're from a magazine that mostly reviewed gear for practicing/professional musicians. 90% of musicians don't change the patches on their instruments at all. This is a highly niche, technical series that doesn't cater to all of their readership, but fills in one of its niches solidly and expertly!