U-He's Diva is a software synthesizer available for download that offers four different oscillator designs, each of which models storied analog modules of yesteryear; from Mini-Moog to Jupiter to Juno, this soft-synth aims to recreate classics as faithfully as possible. It works with Mac- and Windows-based systems in both 32- and 64-bit modes, though be forewarned: Diva is quite CPU-heavy, especially in "divine" mode, which provides zero-delay feedback filters and signature tones that have found their way into rigs of many pro-audio producers and amateurs alike.
Other modes—such as "draft" and "fast"—allow for quicker experimentation with fewer hiccups along the way, so it is indeed possible to experiment in production stages and then render the synth in "divine" mode to audio within your DAW, thus crystallizing its best tones once you've finished tinkering around.
Diva comes with over 1200 preset patches, all of which can be labeled "favorite" or "junk" at your discretion. Different patch templates based on individual pieces of gear will change the graphic interface, and every template hosts a multitude of modulation options, from LFOs to VCFs to ASDR envelopes. For additional processing, be aware that any knob whose label sports a downward-facing arrow symbol houses a drop-down menu for selecting many different modulation sources.
At the bottom of the GUI sits an uncomplicated series of global parameter sections, including tuning, amplifier & pan, and on-board effects. Here are multiple tabs for different windows as well, including modification (rectify, quantize, et cetera), trimmers (with more individualized offset options than the oscillator's controls), an oscilloscope, and the aforementioned preset patches library. Also, Diva supports MIDI-learn, so you can affect and automate individual controls within the plug-in via MIDI messages after assigning them to whatever hardware knob or slider you wish.