I've been using synthesizers for many Many years and have owned (and still do) Lots of hardware. The advent of computers being fast and complex enough to do synthesis is a huge boon to anyone who wants to make sound, from music to especial effects to well . . noise. (hey, noise can be fun!)
Because I continually search out new and different sounding synths and various sorts of sound producing applications, I have amassed a rather large collection, many of which are freeware.
So, if anyone is interested in making some sound waves for whatever reason, I will start putting links here so you can download and play with these pieces at your leisure. Some will be for making music - real music synthesizers, while others will be more on the experimental side.

To start with, here's one call Granulab. This is a sort of experimental way of making sound. You can read about it at the link. You'll need some wave file, any sound will do, to load into it and then play with the controls and see what it does.
Granny - as gray as they come

Hope you enjoy it!
Ken

Here's one with which you can paint an image then render the image into sound! This one's really fun!

http://hem.passagen.se/rasmuse/Coagula.htm

Ken ~

Some music synthesizer applications exist as "plugins". They are basically dlls that require a Host program from which they can be used. One of the main forms or formats is the VST format, or VSTi (for instruments). There are other formats - DXi, RTAS, etc. but VST is the most used that I've found.
Anyway, here's a freeware host program called Cantabile. Once installed you can load plugins and play them on the keyboard at the bottom. If you have a midi keyboard you can use it to control Cantabile as well. You can record what you play if you like, and save it for later play back.
There are lots of Fabulous music (midi) sequencers that act as plugin hosts such as Sonar, Cubase, Logic Pro, Acid Pro, Ableton Live, Nuendo . . . it's a long list. But Cantabile is free and has the features you need to check out plugin synths. Find it here:

Topten Software

There are others, if you're interested. Just search for 'free vst hosts' and you'll find a bunch of them.

I'm telling you this because some of the synths I'll direct you to are plugins that need such a host. There are some really fine instruments among them that I've used in my studio. The best part about them: They're Free!

Ken ~

Brilliant thread Ken !!! i will be having a good fiddle myself

Ok, folks. Here's one of the very Best of all free synths. In fact, it's not just one but several. They come in more expanded version if you pay for them but the freeware version are Very capable. I'm talking about all the neat products from H. G. Fortune, master small synth builder.
NOTE: these are plugins. You must have a host under which you can run them as explained above.
As I said, there are a group of them: Umbra, X-WoF4, Protoplasm, Laser Blade, but I think the one that stands out is called STS-26. It's predecessor, STS-24, is also very good and I believe you can get the full version of it for free. STS-26 has some more features and it's freewware version comes with two voices; the full blown version has eight. Personally, I think two is enough - the rich tonal quality of this fine piece is so full that I'm not sure what I'd do with all those voices.

Anyway, get them here:

Algorithmic VSTI musicsytems by H.G. Fortune

One more thing about H.G. Fortune's synths: they were made with free software you can get for yourself. More about that next time.

Cheers!
Ken

Nice thread, Ken. Worth some karma!

Dave

Thanks Dave!!