FIG. 1: The ImpOSCar settings as heard in Web Clip 2 have a deep, square-wave sound. Only one oscillator is on.
The key to programming convincing synth-bass sounds is simplicity. I use one oscillator with a medium-width pulse wave and a lowpass filter whose envelope has a quick attack, a medium to quick decay (depending on the tempo), and a quick release. The volume envelope's sustain level and decay time depend on the style of music. For R&B and hip-hop, I use maximum sustain; for ballads and gentler music, I use less sustain to leave room for the other instruments.
My favorite synth for bass sounds is my '70s Minimoog with its MIDI retrofit. The inconsistencies in analog circuits produce subtle variations in the sound that keep the ear interested. As an alternative, I frequently use GForce Virtual Instruments ImpOSCar or Access Music Virus Indigo virtual synth plug-ins. Because the programming of the bass sound is fairly simple, the choice of synth is quite important. Web Clips 1, 2, and 3 realize the same bass line using similar settings on the Minimoog, ImpOSCar, and Virus Indigo.
Trying to concoct massive bass sounds by layering multiple synthesizers almost never works. The multiple attacks blend to make one fuzzy attack, and because of the phase differences among the synths, the low end is inconsistent. I use one synth with one oscillator. I have combined multiple bass tracks by recording four passes of my Minimoog playing the same MIDI part with the same sound. In that case, the attacks lined up and the analog oscillators' subtle differences in tuning were enough to spread the sound just slightly. The bass sound in Devo's “Whip It” was created with multiple Minimoogs linked together.
A bass sound that works well in a mix usually doesn't sound good by itself, and a bass sound that is complex enough to sound good by itself often takes up too much room in a mix. Therefore, it's a good idea to program the bass sound while the track is playing. When I record MIDI, I play the part with a sound that I know is close, and then I tweak the sound as the MIDI sequence plays back. I may even change the bass sound during the final mix.
Different styles require different bass sounds. For hip-hop and reggaeton, the sound starts with a sine wave or something close to it. For example, a square wave followed by a 4-pole lowpass filter with a low cutoff frequency is similar to a sine wave but has more definition. Experiment with resonance as well (see Fig. 1). For pop, rock, and ballads, a sine-wave-based sound sometimes works, but you might also try a pulse wave with the filter more open. For those styles, use a slow decay.
For dance tracks, use a brighter sound with a more open filter and even multiple oscillators tuned in octaves. To avoid phase problems when using virtual analog synths, use little or no detuning between the oscillators. When using a true analog synth, sync the oscillators. When the bass sound needs to be bright and function as a midrange part as well, use four to six oscillators tuned in unison and pan them widely. In dance music, the bass usually has a quick decay.
For a more fun bass sound, try increasing the filter resonance and modulating the filter cutoff frequency with a MIDI controller (mod wheel, pedal, or some such). Work the filter modulation with one hand (or foot) as you play the part with the other. (See “Making Tracks: The Low Road” on p. 66 in this month's EM for a description of how to use a filter plug-in to add expressiveness.)
There are times, of course, when a simple sound doesn't work. You can stack oscillators, combine synths, and open your filters wide with a mix that has little more than the bass line. Experiment with hard-syncing the oscillators, and then modulate the pitch of the synced oscillator with an envelope, LFO, or mod wheel. Try using samples meant for something else — electric piano or pitched drum, for example. In short, be as creative as the sonic space allows.
Steve Skinner has worked as an arranger-programmer for Celine Dion, Jewel, R. Kelly, Chaka Khan, Bette Midler, and Diana Ross. He arranged the musical Rent and coproduced the cast album.