Sylenth1

This is very powerful software. It is one of the very first to be able to compete with the quality of a hardware synth. It can sounds just as good, but it is much cheaper. The program was designed from the ground up to be efficient and to produce the highest quality sound possible, but it also runs smoothly on almost any hardware and doesn't overwhelm the system's resources. 

Features:

• Play up to 512 voices at the same time. These voices will sound great no matter what their frequency is. As with all sounds that are produced with this program, they will sound clear and sharp in the finished product.
• 2 filters with 4 sections each. They are designed to sound just like a real filter and produce an amazingly warm sound.
• 7 high-quality sound effects, which also sound great and include an Arpeggiator, a Distortion mode, a Phaser, an option for a Chorus and a Flanger, an Equalizer, a Delay setting, a Reverb setting, and even a Compressor. The Arpeggiator has 10 different modes, which allow you to modify the pitch, velocity, and hold. 
• The program is highly optimized to deliver the best performance without using too many resources of the CPU. It even has a setting to automatically turn off any features that aren't being used.

If you are looking for a program that can create Synth sounds, this one is a great choice. The cost is reasonable and it runs smoothly on even modest setups. If you try this software out, you will see why it has been one of the most popular programs in its category for quite some time.

The program uses minimal system resources