Xpand!2

As with AIR's other synths, don't let the low price fool you. This is a powerhouse.

It's a virtual ROMpler, a "workstation," great for sketching out ideas.

The thing is, the sounds (over 2000 presets) are so good that I often start out "sketching" with Xpand!2 and end up using it in the final mix.

Great basses, pads, polysynths, leads. Some very usable drum machines. Excellent arpeggiator.

It's not without a few (slight, IMO) weaknesses. The orchestral sounds are not something I'd ever use in a final production, but that's to be expected. Orchestral samples take up a huge amount of space. Still, they are sometimes usable when layered with synth sounds.

The GUI is not resizable, so if you're on a 4K monitor, it'll look pretty small. Not a big issue because it's a ROMpler, you use the presets.

The underlying code hasn't been updated in many years, but this actually works in its favor: it's very resource-friendly.

A smashing deal whenever it drops below $10. I think my licenses (I have multiple for my various DAW systems) were purchased for $5. Whatever, it's worth many times that.