Virtual Synthesizers are programs of working synthesizers that are able to be operated on computers, iPods, iPads, Android Tablets, and more.
Virtual Synthesizers come in various types of programs. Most programs can be found on the computer, and are available for download. Others can be found on the internet; these are strictly for online usage.
The App Store for Apple Technology holds a few programs with synthesizers. While very few record or save what you make, some manage to "Embed" or "Memorize" your patterns.
The Android Market is very similar to the Apple App Store, only having more free applications, as it is a free market.
The most common of the Virtual Synthesizers is the mass computer program FL Studio.