When you curse loud music played by your neighbour, what’s really bothering you is the low frequencies.
Bass cuts through walls more than any other frequency and can cause a slight tremor. Bass has two primary uses in music, for rhythm (or movement) or for dramatic weight. Rock and pop music often interlocks bass notes with a Kick Drum to create a high intensity rhythm, ideal for dance. Orchestral music has a wider variety of instruments that provide a low-end. Aside from an upright Double-Bass, there are the bass notes on a Piano, a Cello (a little higher up the frequency) and low-end brass or woodwind instruments like Tubas or Bassoons, which are also closer to the mid-range of the frequency spectrum.
Bass is the signal you will feel most physically and outputs at any frequency below 200Hz. The lower you go, the less audible the bass signal becomes (below 20Hz), however, decibels are still registered, so your body will feel vibrations, without hearing anything. Electronic Dance Music (EDM) can push bass frequencies right down to under 70Hz (or sub-bass). The lowest string on an Electric Bass Guitar is just above 40Hz and the lowest key on a Piano (A) is just above 25Hz. You definitely need special subwoofer speakers to hear very low frequencies. A good quality set of open-backed headphones will also ensure you get a full frequency range.
Bass in music outputs frequencies below 200Hz, any frequencies below 70Hz are called sub-bass, anything less than 20Hz is inaudible to the human ear.
I often record with an Electric Bass Guitar, because I like the roundness of the notes and I can be more percussive in how I play. If I want a fast, metronomic bass rhythm (unless I am bass virtuoso Bootsy Collins) I’ll use the keyboard to create a sequence of notes, then loop it. Playing bass guitar is more demanding physically than a 6-string guitar. I use two or three fingers to hold a string down, doing most of the work with my pick hand. I began learning bass with a guitar pick, I like the sharper definition you get when recorded. Though, recently I switched to a muted, finger-style bass. It’s a different sound altogether, the softness pushes the bass into the background, to create more of a pulse-like effect.
Electric guitarists use lots of treble, especially rock players, because the notes cut through everything else, sometimes even dominating the vocals. When I am mixing an electric guitar, I will cut all the bass frequencies below 70Hz, which provides more space for bass instruments. I’ll push rhythm guitars to the side of the stereo spread, left and right. Then I put the Bass Guitar and Kick Drum right in the centre of the stereo image. I predominantly make rock-orientated music, so I like the rhythm and percussion to be well defined and heard. There are occasions where I’ll push the bass to one side, if I am using two bass instruments. For example, I’ll used a sequenced Synth Bass and Bass Guitar on the same track, because I like how they interlock rhythmically. I then need to reduce the low-end with EQ on all bass instruments, to reduce inaudible decibels, so the mid-range cuts through.
Basic stereo set-up for backing track, bass and kick drum are centred, rhythm instruments to the side. Lead or solo parts (incl. vocal) are centered.
The hardest frequencies to control when mixing are at the low-end. When too loud everything can sound muddy. Also, because frequencies below 50Hz are almost unheard by the human ear, you can be fooled into thinking a mix is too quiet. So you have to monitor your frequency meter to keep control of the low-end decibel reading. EDM music is challenging because the kick drums are often in the sub-bass region of the spectrum. It’s a matter of personal taste and musical genre. I have dabbled myself with EDM beats, wrestling with the kick sound, trying to tame it, soften it. Because, as a rock musician, I am used to drums in the mid-range. There is more air between an acoustic drum kit and the microphones that record its sound.
My own music often has a beat, so I will remove a lot of the sub-bass information below 70Hz, to make room for my guitars. I dial down the bass EQ quite a lot and push up the mid-range and treble. However, I will push up the low-end frequencies of the guitar if there are no drums. I like my acoustic guitar parts to have lots of body, so will only take out inaudible frequencies. There are tricks you can do with Reverb too, that increases the presence of instruments, particularly bass. Reverb will make any instrument sound bigger! So you can fool listeners into thinking they are hearing a really big bass sound, when in fact it’s the Reverb that gives the illusion of increased presence. Useful when you have to remove the low-end in a busy a mix.
FabFilter provide a great Pro-R reverb plugin with limitless possibilities for giving your recorded music presence and scale. This example is a setting I often use for Bass Guitar.
Vinyl is of course very popular again, however, vinyl records cannot cope with an overload of bass and have to be mastered differently to CDs or digital audio, otherwise the needle would just jump about on the turntable. I am a big Reggae fan, but this type of music can suffer from a loss of low-end feel when mastered for vinyl – though a little reverb trickery can soon fix that. Early Reggae, recorded in the 1960s or 1970s, often sounds weaker on vinyl (and treble-drenched radio). DJs (Sound Systems) compensated by cranking up the volume of their stereo equipment and used additional amplifiers and EQ control to boost the bass. Dub Reggae really doesn’t work when played quietly! And you will really struggle to feel the bass, if listening to Reggae on cheap stereo equipment.
I have always liked lots of bass in music. But it was quite a steep learning curve, controlling the low-end, once I began recording my own music. Perhaps it didn’t help my tinnitus a great deal, because my earliest attempts at recording always had the bass way too loud. I’ve spent countless late nights trying to figure out why I was unable to increase the overall loudness of my tracks. The problem was I had too many inaudible low frequencies that were eating into the decibels. My tracks were clipping into the red, but sounded too quiet. I couldn’t push the volume up any further. But I persevered and studied other recorded music more obsessively. Why do their bass instruments sound so big and dominant? How did they get the other instruments (like guitars) to sound so bright and clear? The secret was controlling the low-end, removing inaudible frequencies and getting creative with Reverb.
Recorded music is weaker without low-end presence
I am writing from the perspective of modern rock and pop music, where bass is used as a rhythm or percussive instrument. Of course, popular music is largely derived from the Blues and its offspring Jazz (or Ragtime as it was originally termed). For me, the best examples of Electric Bass Guitar can be heard in Jazz, Soul and Funk music, which greatly influences modern EDM, including House, Techno et al. Bass in orchestral music provides heavyweight drama and presence, as heard in Beethoven or Wagner. Many contemporary film and TV soundtracks are a crossover between scored, classical pieces and electronic ambience (see Vangelis), where the bass is synthesised to create a grainy, machine-like warmth. There are so many fun things you can do at the low-end, that the listener can physically feel.