SynthEdit is designed for making music. At the simplest level, maybe just creating a short sound effect. At the other extreme it can render a complete performance with several virtual synths, drum machines and effects. SynthEdit is modular, to get the most out of it, be prepared to do some assembly yourself. It's not hard though, and the flexible nature of SynthEdit puts YOU in control. For example most electronic instruments have limitations. They may have limited Voices, Oscillators whatever, with software synthesis you are only limited by the power of your PC. In fact by using SynthEdit's 'render to disk' you aren't even limited by your PC's processing power.
If you are happy making music that sounds the same as everyone else, there are plenty of instruments with preset sounds, there are plenty of soundcards with great built-in sampled instruments. If you want something unique, or off-the-wall you need to get your hands dirty.
SynthEdit is modelled on the classic Analogue Synthesiser. Before the days of pre-set synthesisers, electronic musicians had to create sounds the hard way, by assembling 'modules', boxes that created or modified sound in some way. Wires called patch cords connected the modules. Although this was time consuming, you had complete freedom in designing your sounds. SynthEdit brings back the 'Analogue' synth, and adds features from the MIDI era.
The basis of everything is the 'module'. The coloured text represents 'Plugs'. You connect modules together by clicking and dragging between the plugs. The audio signals enters though the plugs on the left, and exits via the ones on the right.
Not everyone wants to mess around with modules just to make music. SynthEdit comes with pre-built synths ready to use. The idea is to connect these up the same as you would instruments in the real world...
The black lines represent audio or MIDI cables. The green box icon 
indicates
a 'Prefab' or 'Container' module. It encloses a collection of modules. This
example connects the PC's MIDI in port to a virtual synth, then sends the sound to your
speakers. You then use an external keyboard to play the soft synth. Try loading the
example file 'live.se1' to try this out.
Another Option is playing a MIDI file.
This example plays one channel of a MIDI file. To simulate several instruments you cut and paste the Poly Synth several times.
There are two ways to view your modules. Firstly, the STRUCTURE view, you deal with this when you are designing your synth. It shows all the modules and their connections..
and the CONTROL PANEL view. This shows only the synth's controls. This is what you deal with when you want to play the synth.
Both are views of the same objects. To choose the view, Right-Click a Container and choose either 'Structure...", or "Panel Edit..".
With Software synthesis, it is very easy to overload your PC's processing power. SynthEdit supports writing your music to a Wave file( you wait while the music is recorded to Hard Disk, then play the Wave file afterward). This is not as interactive as real time output, but you're no longer limited to just one or two synths, you can have as many as you like, plus drum modules, effects etc, and can record at a high quality sample rate like 44kHz or better.