Enhancing the perception of bass sound and its timbre can sometimes be a fine process to look at. This article will present some general principles to consider, not only in sound design and electronic music production, in mixing music also.
Before we look at techniques, let's introduce some essential knowledge about timbre.
Harmonic Slope
While we can define bass as a single low frequency, typically between 60 and 250hz, the timbre of the bass can actually occupy the whole audible spectrum. We know that Bass is more of a Pitch, lending to having tailored musical instruments such as Bass Guitar, Double Bass, Tuba, etc. Each of these instruments are designed around the same low pitch, with different timbre or tone quality.
When we look at the timbre of the bass as the general frequency curve, we will also notice a tendency in the spectrum. We can speak of Bass as Powerful or Dull, Full or Thin, Dark and Bright, to name a few examples. A Tuba for example gives a much sharper, brighter timbre than a Double Bass, and a soft pluck of a guitar gives a duller sound than a strong pluck.
Let's now move to synthesis. To look at 4 common Synth Oscillator spectrums, we can learn about their impact on bass perception.
- Sine - A sine wave contains a single, pure frequency. Alone it is the most basic and dull, but can be a great building block for new or simple bass sounds.
- Square - A Square wave contains only odd Harmonics. Although it is a much bigger sound, it does not sound 'full', or contain Octave overtones. Due to its flat wave shape, it can sometimes appear louder.
- Saw - A Saw wave contains all (odd and even) Harmonics, and therefore is the richest sounding wave to use in synthesis. The digital saw wave generated from Absynth has overtones with a 6dB/Octave slope, but like the Square, the timbre of filtered Saw waves is easily identified.
- Impulse - Like the Saw wave, the Impulse ('Supersaw') wave contains all Harmonics, but with a flat Slope. We will instead hear a Bright, buzzy sound. The Fundamental, or Bass sound actually becomes 'thinned' out.
The fundamental bass becomes weak with a slope any flatter than the Saw wave. Therefore, a Saw with -6dB trend is best for a rich, fundamental tone. See Fig. 1 Below.
Fig.1 - The analysis of simple Wave Spectrums with same Headroom. The Saw wave provides strongest Phantom Fundamental with a -6dB bass slope.
The Phantom Fundamental
With the aid of these high frequencies, we can hear the fundamental frequency as a distinct pitch, across the spectrum. The more overtones in the spectrum, the more likely our ears will identify and the fundamental tone. However, much like the fundamental frequency, the lower frequencies are more crucial in the main body of the sound.
Due to the uniform harmonic relationship, the frequencies are perceived coherently as one fundamental frequency. Yet, when these lower frequencies are filtered or stripped away, the apparent pitch is known as the phantom fundamental. This phenomenon, also known as ‘residue perception’ can be defined as such:
When the root bass is perceived, without the fundamental frequency present.
This sometimes occurs in music that is played in lower quality speaker systems or small earphones. Even tinny sounds heard from a distance may have some identifiable bass tune.
If we use the pure bass frequency like a sine wave, a focused part of the spectrum is then just an isolated frequency, which has less definition. To widen the perception of that frequency, we add definition by adding more integer harmonics.
For a comprehensive video demonstration, please watch the above video thumbnail.
Using a 'full synth sound' as a bass is often challenging to mix into a song: If the overall sound is so full and present, then there tends to be less need, or less energy available for more instrumentation.
Yet, this has led to new genres of Electronica such as Drum 'n' Bass, Dubstep, EDM, among others. How much spectrum is in the bass can illustrate how important it is in the track.
Techniques
The tips here can be applied with most synths. They will offer some insight into what makes bass sounds so impactful. Each technique is a matter of taste to use within musical expression.
1. Pluck the Sound & Enhance the Transient
Give the sound a strong transient or pluck style. This will cue the listening of the tone and enhance the closeness of the sound. The transient stab can be created with a sharp Attack Envelope, combined with a fast Filter or FM Index Decay. Plucking sounds are effective and musical, but also have a similar energy to impact sounds.
2. Add Harmonics to the Fundamental
Add a Saw Oscillator or other layer to the mix. As outlined in the beginning of this post, a Saw wave offers a full, harmonic spectrum. In Subtractive Synthesis, this offers great spectral depth and presence to work with. All frequencies related to the fundamental bass are reinforcing and complimentary. Layering other sound also offers a different character.
Secondly, let's take a closer look at the subharmonic aspect: we can also introduce a different subharmonic relationship by tuning down an Octave. This thickens the sound, and it is what contributes to the use of sub-oscillators.
Wave’s MaxBass plugin, as well as in my case, Logic Pro's SubBass plug in, have two filters for ‘high and low’ of the spectrum, which can be balanced together. In the above video (Part 1) you can watch how mixing both low frequency harmonics and high harmonics adds presence to the signal, but that same presence is related to the subharmonic wave.
3. Use a Notch for Contrast
With the harmonic slope in mind, a notch filter in the upper-bass can still help reduce boominess and add contrast. This technique is common in drum and bass music, as well as sweeping the notch to create exceptional movement of the bass sound, but while returning to a prominent, low-end sound.
4. Use Shorter Notes for Impact
To add further weight, especially to the plucking style, try shortening the Release time. This creates an effect of stopping the sound, which gives a heaviness. It is mainly a way of contrasting the existing sound; by shortening its duration, it can appear stronger or faster. In some Trance music for instance, an arpeggiator may also perform shortened stabs for extra tension, followed by extending the time and/or release envelope for a relaxing effect.
Generally, prolonging the sound will gradually diminish the impact of the bass due to ear fatigue.
5. Consider Modulation
Modulation can enhance any of the above ideas. Below are some examples:
- The Reese Bass creates strong beating effect with two or more detuned Saw oscillators. This actually creates sub-bass movement through the entire spectrum. The wobbling pitch has a pulsating bass effect alone, which only requires two Sine waves of different frequency.
For a demonstration of these techniques, you can view Part 2 of the video above.
- Unision similarly leads to a richer spectrum, with 'fatness' and a more slower, but moving, phasing sound.
- Using the LFO for Tremelo, or Filter wobbles gives greater control over the speeds of bass surges.
- Pitch modulation and Pitch envelopes are also a more direct way of influencing the whole sound, along with its basic timbre. The timbre does in fact change with larger pitch sweeps.
Overall, these techniques are useful to varying degrees and can even give body to higher notes. It is fascinating how timbre is reflected not only in the frequency domain but also time domain - they are linked.