A cool way to create unique synth sounds is to use a short, looped portion of a sample as the basis for a “sample-synth.” By selecting a single cycle of a waveform in a sampler, then looping the cycle, you can essentially turn the sample into an oscillator, and the sampler into a simple synthesizer.
Selecting the Waveform
Start by selecting your source sound. You can use really anything as the base sound for your sample-synth: a field recording, an audio file from a sample pack, your own voice. Drop it into the sampler, zoom way in on the waveform, and scroll through the sample until you find an interesting-looking waveform cycle. Select the cycle using the sampler’s loop points, making sure that the loop points are both exactly on top of zero crossings (points at which the waveform’s line crosses the horizontal line that bisects it). This prevents clicking and popping that could otherwise occur when the sampler restarts the cycle. Set the sampler to loop the selected portion of the waveform.
Tuning the Synth
Next, you’ll (probably) need to tune the sample-synth. Load up any VST synth on another channel, set it to play a simple sine wave, and arm both the sample-synth and the VST for recording. Play a C3 note and listen to the difference in pitch between the two instruments, then adjust the “Root Note” parameter on the sampler and play it again. Keep adjusting the root note until the two instruments are playing at the same pitch (if you’re having trouble matching the pitches, use a spectrum analyzer plugin to help determine the difference between the two).
With your “oscillator” set up, you can move on to adjusting the rest of the sample-synth’s parameters. Configure the amplitude envelope based on what type of synth you’re making (slow attack and full sustain for a pad, for example, or fast attack and no sustain for a pluck-type synth). Filter out unwanted frequencies; use the filter envelope and/or an LFO to add movement; add velocity-modulated parameters. Finish off the sample-synth by adding effects like reverb, compression, and delay.