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.
Beat creation and performance instrument features 16 pads and onboard step sequencer