Ableton have let this one out without too much of a hullaballoo - its an online (browser based) course in basic synthesis, with some excellent jacascript and web programming (including web MIDI).
Titled: Learning Synths, it covers the basics, right from oscillators and control of pitch and amplitude to filters, envelopes and LFOs. A great resource for beginners and ends with a playground section with a fully operational web based subtractive synth to play with.
Its all browser based and we're told will work on desktop, tablet and phones too. Good work.
Oh yeah, its free.