This is the second installment of a series of articles detailing how to program tight, effective analog bass lines and some of the best synths for achieving good bass sounds.
One of the well known “secrets” of getting a good bass tone is to use a synth that is optimized for creating bass sounds. Even the greenest of novices is often aware of the many famous “bass synths” such as the Moog Minimoog, the Juno 60, the Korg Mono/Poly or the Oberheim SEM-based synthesizers. However, good bass tones are not just restricted to these synths alone. In this installment we are going to examine some of the factors that influence a synthesizer’s design that makes it a candidate for a “good bass synth.”
Not all synths are created equally when it comes to producing quality bass sounds. But what are the factors that contribute to a synth being a good bass machine? Let’s examine some of the common features that often lend itself to creating quality bass sounds.
A crucial area of determining the effectiveness of a synth for bass tones is the envelope speed, which should be very fast. Quick, tight envelopes lend themselves well to punchy, “attacky” sounding bass lines; synths with average or slower envelopes are unable to adequetely create these sounds and will be very limiting. In general, the speed of a particular synth’s envelopes are open to speculation and a great deal of subjectivity. The best way to test a synthesizer’s envelope speed is to play it yourself and experiment with different attack and decay settings for both the amplifier and filter. In general, on a synth with fast envelopes you should be able to set a modest (perhaps 15-20% of the knob’s travel) amount of attack and not lose any punchiness, but instead gain a zipping, ripping rise in amplitude or filter movement.
SCI Prophet 5: Along with the Minimoog, the Prophet 5 has some of the fastest envelopes on any analog synth ever made.
As a general rule of thumb, most hardware envelopes, such as found on any synth made in the 1970′s and early 80′s, will be pretty quick. Likewise, software based envelopes such as found on the Oberheim Xpander or Matrix 12, or the Sequential Prophet 600, tend to be noticeably sluggish. Most modern virtual analog synths have pretty fast envelopes now, due to the increase of available computing power for the software and the keyboard scanning. (Due to this phenomena, many late 80′s and early 90′s synths have a sluggish feel to them because of overworking the CPU for both sound generation and keyboard scanning. The Roland D-50 is a famous example of a synth whose envelopes feel slow due to the time it takes the microprocessor to read and scan the keyboard to trigger a note.)
Two synths that you should definately check out for hearing fast envelopes are the Moog Minimoog and the Sequential Circuits Prophet 5-both of which have incredibly fast envelopes, probably somewhere in the vicinity of 1 millisecond or less. On the other hand, listen to a Roland JX-8p or Sequential Circuits Prophet 600 to hear the effects of slower, sluggish envelopes. After hearing for yourself the differences between these synthesizers, you can better evaluate envelope speeds on other synths that you encounter. Once again, measuring envelope speed is often very subjective and requires you to experiment and listen.
Korg Mono/Poly: The Mono/Poly’s fearsome quadruple oscillator power and bass compensated SSM filter can create stunning bass tones in the right hands.
Besides envelopes, the filter is probably the next most important factor for determining if a synth has a good bass tone. Generally speaking, you want to have a 4 pole/24 db low pass filter for most bass sounds. Normally, the 2 pole/12 db low pass filter does not contain enough filtering to produce strong bass sounds, although the Oberheim SEM and OB series is a clear exception to this general rule. For the most part, you want a 4 pole low pass filter in your synth, which is, thankfully, the most common type of filter found on analog synthesizers.
Another critical factor of filters is how the signal is fed into the filter itself through the analog mixer. For some synths, such as the Minimoog, a subtle amount of clipping is introduced at higher mixer setting which produces a warm, distorted sound that the Mini is famous for. Other synths, like the OSC OSCar, are also capable of overdriving the filter with a strong audio signal. In general, unless you resort to some type of modification, most analog synths do NOT overdrive the filter at all, which is a shame.
There are a number of other features that can help you assess a synthesizer’s filter for good bass sound creating possibilities such as the presence of variable keyboard tracking, the ability to disengage the filter from tracking the keyboard at all, precise control of filter movement by the filter envelope (or envelope if the synth has only a single envelope), and odd features that allow you to modulate the filter by its own output. Modulating a filter by its own output creates excellent biting, edgey tones such as found on the Pro-One or Prophet 5.
Studio Electronics SE-1: Easily one of the most powerful bass creating rackmounts, this monosynth has all the capabilities of a Rivera Music hot-rodded Minimoog… plus more!
Although both the filter and envelopes are perhaps the most important areas to consider when evaluating a synth for its bass creating capabilities, the oscillators too play a large role. Typically, you want to find a synth that has at least two oscillators with good mixing capabilities that allow you to turn one or more of the oscillators off; this allows you to have access to a greater number of tones and the ability to mix different waveshapes together. Another good feature to have is the ability to set different pulse widths for each oscillator-strangely enough, this is a seldom seen feature. At the very least, look for a synth that allows pulse width modulation by either the LFO or envelopes. Synths that feature triangle and sine waves are also good for producing bass tones, and offer a wider tonal pallete than the typical sawtooth and pulse/square wave options. Triangle waves are especially good to use as a “sub-oscillator” an octave or two underneath the fundemental pitch (the Korg Mono/Poly excels at capers such as this).
Another important factor is the “gutsiness” of the oscillators themselves-which can be, once again, highly subjective. However, if you compare a number of analog synths this characteristic will soon become apparent. Look for strong, harmonically rich oscillators that have presence without becoming overly strident in tone. Some good examples of particularly strong sounding oscillators include the Oberheim OBXa, the indomitable Minimoog, the Korg Polysix and the Roland Jupiter 8. As virtually all analog synths subscribe to the subtractive synthesis model (starting with a harmonically rich waveform and then subtracting from it by use of a filter) having gutsy filters insures that your tone will remain strong and punchy after it has been processed by the filter.
This article has looked at the three basic features common to most famous “bass synths” such as fast envelope speed, proper filter implementation, and versatile, gutsy oscillators with a flexible mixer. By carefully choosing a synth that is optimized for creating bass tones you will have gone a long way towards overcoming some of the problems with creating a good bass sound. It is amazing how much your playing and sound will improve by playing bass lines on a synth proper for the job.
Until next time.
James Meeker
Pro AudioUnit and VST plugins
