I often get to the stage where I get sick of a various software synthesiser that i'm working with. Maybe it's the tone of the synthesiser itself, or maybe its the layout and the options always being the same and leading to the same results. Don't get me wrong, it's good to have mastery over your tools and be able to get the most mileage out of them, however the other side to this coin is that having a range of tools is useful for generating different results. Now you may simply want to switch synthesiser, and thats something that often works for me.
However, most software synthesisers are usually comprised of the same parts, an oscillator section, filters, an assignable LFO and maybe some effects. You're limited to the waveforms included with the synthesiser, and until you start resampling you are also limited to it's effects. An intersting way to go about designing a sound that doesnt rely on a synthesiser is to use a sampled waveform, as is done in granular synthesis. Granular sythesis is complicated, however below is a simple and straightforward guide on how I personally do this. As usual, i'd like to make you aware that this isnt necessarliy the right or the wrong method of doing this, but simply my method.
Step 1: Acquire Sounds
I go about this by using my smartphone. I have an app on it called iTalk, and it lets me record sounds and sync them straight to my Dropbox. I've also recently com accross a huge library of sample accurate waveforms sampled from analogue synthesisers, instruments, the human voice and other places. Anything is fair game if you can get a good result from it, you could use a kick drum sample or sounds from your collection if you like.
Step 2: Tune and Crop Sounds
In most cases you'll need to tune the waveform so that when you do play it back it will be chromatically accurate, that is to say if you put it in a sampler and play it with a MIDI keyboard then the keys you play will generate the correct note out of the sampler. In order to do this place a spectrum analyser on your sound and take note of where the tonic peak of the sound is, wherever the peak is equals the key your sound is in. Next cop the sound, you want one cycle of the waveform, and you'll need to be as accurate as you can here. Below is a picture of a kick drum that I placed into sampler and cropped so that one cycle of the waveform played back repeatedly.
The sustain mode is how I can get this small portion of the sample to loop repeatedly. Play around with the forward and reverse option, which gives you a completely different sound.
Also worth noting is that while you do want to be as accurate as possible if you want to stick to the character of the original waveform, playing around with the start and end times can sometimes yield some interesting results and add more overtones to the sound. Howvere just be aware this can change the pitch of the sound.
Once you have cropped the sound to your liking you should pitch it up or down until it's in the key of "C" so that when you play it as an instrument with your MIDI keyboard, it is chromatically accurate as stated before.
Step 3: Process the Sound
Here's where things start to get really interesting and where Sampler in Abletoin really comes into it's own. Now you can, using the other tabs in sampler, start to add things like filters, envelope and LFO modulation. You can also create a copy of the sound, and detune it slightly against the original so that it fattens up the sound. You could add a pitch envelope (see below) so that your sound rises for a couple of octaves over a set amount of time everytime you play a note. And of course you can add all the external processing you want. For basses, the obvious choices would be saturation, distortion and filter modulation. However if you were making an ambient sound you'd set a long attack and release time on the volume envelope, and add in some time based effects like reverb, delay or a chorus.
Protip: Choose your sounds carefully and based on what you want the results to be. If you want to make a bass then yeah, go for a kick drum or a recording of a car engine or something. But if you want to make a pad or lead you might be better off using a recording of a bell or a chime for example, and granulating that instead.
Edit: Here's a good video that concentrates on this method and using it to make an ambient sound that I just found, check it out...