Anatomy of a bass sound
The idea that sound waves can be experienced not just through hearing but other bodily sensations too is not new – just standing in a club will tell you that. In fact, it’s likely that our ears have evolved from our fish ancestors’ lateral line, which is an organ used to sense water pressure changes. Further, there’s a belief that you sense low frequencies at different points on your body: the trouser-rattling ultralows, going up to the more sensual lower abdomen sounds of the 50-80Hz range, through the sometimes nausea-inducing 80-100Hz in the belly, to the hard 100-140Hz of a punching kick drum to the chest.
In today’s music, the bassline overwhelmingly originates from either a bass guitar or a synth. There are a huge range of sounds you can coax out of a bass guitar, from the dull, super-fat sounds of dub reggae, to the bright, distorted and relatively thin sounds of Lemmy’s Rickenbacker. Bass guitars are often just DI’ed, but the contribution of an amp should never be underestimated in terms of saturation, drive and the simple act of shifting air and recording it. In the absence of an amp, there are plenty of amp sim and saturation plugins that can approximate the effect.
Synthetic subs
For creating bass sounds, synths are, of course, a lot more sonically versatile, although they tend to lack the performance imperfections of a good bass guitar player. That’s not to say a bass synth is necessarily soulless, but it’s harder to achieve something that does more than just give you a succession of notes. When all is said and done, perhaps the strongest argument for the use of a bass synth is its potential for producing rib-rattling sub-bass frequencies to really weigh down a mix.
Back in the days of hardware synths, there were a few classic models for basslines: the Prophet-5 and the Minimoog were two favourites, plus the Roland Jupiter-8 and slightly later the ubiquitous DX7, often layered with the Prophet-5 on records by the likes of Michael Jackson and Madonna. Later, the Roland TB-303 Bass Line revolutionised the 90s dance music scene with it’s expressively sinuous sequencing and filtering, and companies like Novation and Korg have since kept the mantle with a variety of excellent machines. Software synths are everywhere now, from models of the classics (Arturia’s Mini V and D16 Group’s Phoscyon, for example) to originals that deliver their own amazing sounds, such as Native Instruments’ Massive and FM8, and u-he’s Diva.
Nose to tail
The sound of the bass guitar or synth follows a similar pattern to the kick drum: with a front attack, or ‘nose’ – mainly composed of mid frequencies, although it can go higher for example on slap bass techniques – followed by a deeper sustain which carries the fundamental frequency (the root note). The number and volume of harmonic frequencies will determine the tone. For example, a dub bass guitar sound or sub-bass synth is almost completely pure sine wave, whereas a harmonically-dense bass guitar part may feature plenty of mid frequencies.
In most instances, the tail of the bass note is longer than the kick, as we need to be able to perceive its tone and melody in order for it to qualify as ‘a note’. Varying the length (and thus gap between notes) is a useful dynamic device: we perceive shorter notes as quieter, so by increasing the length of the notes throughout a piece, the track may start to sound ‘bigger’.
Dynamics-wise, you’ll usually want to keep bass at a consistent level throughout the course of a track, as this will help maintain a consistent low-end weight in the mix. Compression is the obvious processing choice for evening out low-end dynamics, but consider your source sound when deciding how much compression to apply: a programmed synth bass will naturally be more consistent and ‘rigid’ in level, whereas a bass guitar part performed by a human player can vary wildly in dynamics from passage to passage.
But be aware of the dangers of compression, as well. Low frequencies will trigger the compressor first, which can often ruin the front end of the bass; consider using either a compressor’s sidechain filter to prevent bass frequencies from tripping the compressor’s sidechain circuit, or a multiband compressor to target specific frequencies and maintain an even balance between the sound’s attack and its subsequent weight. Saturators are useful here too, because – just as with kicks – you can use them to enhance the harmonics of the attack and the decay, binding the overall sound together with that sonic ‘glue’.