I like crystal a lot for a start, because of it's GUI in diferents tabs. It helps explaining the global organization of a synth, and each voice tab is a pretty simple yet powerfull substractive basic synth. You have two sub menus for algo and wavetables, FM/RM at its simplest, filter and amplifier with their respective envelopes (though the envelopes arn't the typical ones).
And seperate matrix, LFOs and EGs, and when they start to get along with it the mixer tab with crossover etc is pretty interesting.
One last thing I like with it is that a lot of students learned to not dismiss a synth only for the way it looks using it.

This one and tyrell.

for a straight forward vintage style synth with all the usual knobs and routings try TAL's 'Noisemaker' or UHe's 'Tyrell' - both free

for something with more scope try (my fav) 3 freebie synths are UHe's 'ZebraCM', Synapse's 'DuneCM', and kv331's 'SynthmasterCM' (all free with Computer Music magazine - UK)

Did i mentioned that we go more and more in the age of information overflow.

Charlatan, for sure.

I like Clearsynth by xoxos. It has lots of presets which walk you through each function. No mod matrix but it has assignable LFO and envelopes. It also sounds good. I discovered it just after I really needed it, (I cut my teeth personally on the "lovely" A1 synth in the older Cubase... I still have the patches I made and boy are they crap )

+26

Ne'er seen this one before, looks real nice.


Is it o'ersampled?

Seriously, though ...
... start where it (pretty much) all began?



http://elektrostudio.ovh.org/index.php?go=mini

(Numanoid thinks it's worth a hundred bucks. Anyone disagree?)

OD Say is awesome in my top free lead synths along with these.

Z3ta free in cm and in BE but now I have Z3ta+2 and it really rocks
minimogue
prodigius
Tyrell
AT4 free
Xils lab polykb II cm
Scanned synth CM mess with it and be ready to be surprised. I did not like it at first but when you tweak it the sounds are awesome.
Monofury
Tal
Mausynth
Synth1
Zebra CM
Istvan Maestro
ilosynth

Also OR2v is badass as well and the new model mini ditto.

+100000

It is simple enough for a total newbie to learn, it has a great GUI designed by the best, it sounds great so the students WILL want to continue learning.

Another thing i highly recommend is an oscilloscope - for a newbie with no trained ears it is good to see how the sound looks like and how moving the various controls affect the wave.
And learning with 2 senses instead of 1 is also more effective.

http://www.kvraudio.com/product/s_m_exoscope_by_smart_electr onix
http://www.kvraudio.com/product/signal_analyzer_by_rs_met

Which synth do you mean by "OD Say"? I tried looking it up but couldn't find it.

ODSAY from Elektrostudio - follow the link above for the Model Mini.
It's an Arp Odyssey clone (if you hadn't guessed).
And - yeah - 'awesome' just about covers it!

Not freeware but very easy to learn:
- Camel Audio CA5000

Freeware:
- Crystal Synth
- Zebralette (U-he)
- Zebra CM (U-he)

Absolute beginners should look no further than GTG synths

http://www.gtgsynths.com/plugins.htm

Synth1 10 years ago.. Synth1 still today.

It is straight forward and, although a bit boring, I find the Synth1 GUI is grouped in a way that makes it easy to understand.