Surge XT is an open source hybrid wave-table synthesizer with a lot of 3rd party patches available. It was originally developed as a commercial product but was then released s an open source product in 2018.
It is can be installed on Windows, MAC and Linux OSs and is available through the Surge website.
Surge XT is an excellent instrument. Once you become accustomed to its unique routing system it’s fun to program and a good set of useful presets is provided. The pros on Discord have been very helpful answering questions about it.
For free synths –
Vital
Surge
U-He free versions (all of them are really good).
Odin from wavewarden is very powerful.
Vital is also very easy to program with drag and drop routing, and a large number of free presets available from third parties.
Vital is brilliant at evolving pad sounds.
I only have one problem, I like them so I get tham and then suffer from too many synths. I don’t think I will ever buy another synth.
See my post on Vital here.
I’ve been running into the conundrum recently too (too many synths)! I’ve decided basically to learn Vital and Phaseplant inside and out and stick with those two. I may be wrong, but it seems that between the two you can produce just about any sound you want. It’s just too much work to learn 5-6-7 different synths. With some tweaking, you can even get these digital synths to emulate some of the old analog modules.
I think its best to learn one synth really well and then leverage that for learning other synths.
Each one I’ve worked with has taken time. I like presets but often end up editing them. I then save those so I’m gradually building a library of my own.
I just spent a few hours with Wavewarden’s Odin (free, see above) and it has some great features and sounds.
Vital can be wild but in the hands of a good programmer like Eric Bowman it can do normal sounding instruments very well.
Surge is very deep and has a great Discord community for questions and help.
I like all my instruments and I don’t have a huge set-up. I’d love one of the big orchestral packages eventually, but I don’t do that kind of music.