What is "Air?"

[Ted]

I've heard about "air" for a long time, and I have always thought I kind of understand what it is. Today I tried to search for it, and with a name like "air" it returns a lot of results about other more common uses of the word air.

Sometimes after I record an acoustic track, like vocals, or something recorded with a mic, I cut out all of the "empty" parts of a track to eliminate room noise. When I do this, I wonder if I'm eliminating "air" – something that would make the recording sound more natural.

But I also read about "air" as a quality of the tone, or the notes. A sense of space that is created by the room, or by the harmonics. People talk about it reverently like it's fairy dust.

So what is air, anyway?

Is it just a sense of the space, like reverb but more subtle?

What got me thinking about it was this old pedal I've had for years. I've always liked what it does, but I've never been able to really put my finger on exactly what it does. I always think that it can "bring out the best" of my bass tone, or acoustic instrument. But is it just EQ? A low-pass filter on the left, and a high-pass filter on the right? Does it compress?

When I read about it, every description uses vague (to me) language about "psychoacoustics" and "harmonic generation" and "adding air."

[Blooby]

I have no idea if there is a single meaning. I think of reverbs and delays providing air, but I also think an open or uncluttered arrangement and/or mix has some as well.

[Farrell Jackson]

I've always thought of adding air to a track as adding a bit brightness with high eq at 12K or so. For instance, I sometimes create a duplicate vocal track and shelve off below 300hz and add some hi eq so it sounds bight and thin. Then I blend it to taste with the original vocal track to give the overall vocal track some air and presence in the mix. That keeps the vocal sounding full, natural but with added highs, without introducing any eq harshness. I think the bass pedal you have might be doing the same thing internally without having to create a duplicate track.  Describing "air" in a recording is an obscure thing. I'm sure others have thoughts on this as well but this is just my humble opinion.

[Ted]

I think the bass pedal you have might be doing the same thing internally without having to create a duplicate track.

I think you are right. I asked a similar question on Reddit r/basspedals. The question was more about this pedal, and less about the meaning of "air." I got a couple of good responses.

TL;DR: Lows get compressed, highs get distorted, both get mixed with dry signal.

Think of it as side chain eqed parallel saturation. A high pass filtered copy of the signal is fed through a distortion circuit and then blended with the original signal. It basically enhances high frequency harmonics to add clarity.

[64Guitars]

I think "air" is one of those overused and often misused terms that are especially favoured by marketing people. Another is "colour'.

I found this page at LANDR which says:

"Air" frequencies

The very top end of the frequency spectrum is home to an elusive quality mix engineers call "air."

Air frequencies go from the top of the high end around 12 kHz all the way up to the extent of human hearing at 20 kHz.

As with the low sub bass, these frequencies are often more "felt" than heard. But they make a big impact.

Although, how that would apply to a bass pedal is hard to imagine.

I've always thought of "air" as being the opposite of "muddiness". We've all heard "muddy" mixes where it's difficult to hear individual instruments or phrases because all of the individual sounds are clobbering each other so that nothing stands out. Adding "air" makes the mix less muddy so that individual instruments and sounds stand out more clearly. In the context of your bass pedal, I think it means making the bass crisper and better-defined so that it stands out better in recordings or in band performances.

[Ted]

I found this page at LANDR which says:

"Air" frequencies

The very top end of the frequency spectrum is home to an elusive quality mix engineers call "air."

Air frequencies go from the top of the high end around 12 kHz all the way up to the extent of human hearing at 20 kHz.

As with the low sub bass, these frequencies are often more "felt" than heard. But they make a big impact.

The next section of that article was also very interesting:

Hot Tip: The most sensitive human ears top out at 20 kHz, but there are some interesting EQs that allow you to boost at frequencies even higher.

This part of the spectrum is well outside the audible range. But these boosts are so broad that their effects radiate down through the spectrum and cause a subtle but transparent increase in the sense of "air" in the mix.

If your mix is missing this quality, consider emphasizing the air frequencies in sources that contain naturally pleasing high end information.

I've accidentally become obsessed with infrasonics – thanks to my micro-Thumpinator and the discovery that something is adding a lot of hum and infrasonic sound to my recordings (possibly noisy power in Madagascar, or some other interference in my house). I've developed the habit of running a high-pass filter on almost everything I record, using Audacity.

Adding "air" makes the mix less muddy so that individual instruments and sounds stand out more clearly.

Removing the mud may also do the same thing.  Here's something interesting that I encountered recently: After recording the bass part for this song, I listened to it soloed, and it sounded okay – maybe a bit too trebly, but I was going to go with it. Then I ran the high-pass filter to remove the infrasonic frequencies. After suppressing the ultra-low frequencies, the bass part sounded lower – less trebly.

Am I crazy?

Here's an excerpt from the bass part. I used the Bass Xciter on this. The first nine seconds (Part 1) is with infrasonic sounds, the second half (Part 2) is with the infrasonic sounds removed with a high pass filter.

   

I can hardly hear a difference now, but in the mix I swear the bass sounded lower and more defined after removing the lowest frequencies. I can only concluded that (a) I imagined this, or (b) there's some complex harmonic interplay in the overtones that changed the way this sounds in the mix. I'm willing to accept either possibility.

Did subduing the infrasonics somehow give way for the "air" harmonics to rise and better do their thing in the mix? This sounds like sorcery. I probably imagined it. Maybe.

[Zoltan]

I held my air as i noticed others were better at explaining things... But this part about changing something in the mix / EQ / Infrasonic wise & imagining things.

Things get easier as soon as you accept that: everything affects everything!

(Not trying to sound Zen btw...).

[WarpCanada]

I hear it used imprecisely all the time. 

"This track needed more [air, sparkle, definition, smoothness] in the [vague eq band descriptor]".

Plain English Translation:

"I tried the EQ knob X at Y khz, and tweaked it +/- Z dB and it sounds better to me and now I need a word or phrase or sentence that I can use to defend [to myself] my mixing decision".

I think audio TALK is 90% nonsense.   There is not even a clearly agreed upon framework for comparing two reference mixes and saying what changed when you change one EQ knob on one track or on the master.

In the end, these are creative decisions, and to me, air is a useful word for leaving in more room sound, or creating some artificial room sound that you like.   

Tight EQing to remove ALL the noise may be possible, but often lead me to feeling there is "no air" in my mix. But no problem, because you can create your own air. 

I think that a lot of my mixing decisions are to create something that I think sounds credible as a performance in a place.  I want to hear evidence of reflections (early, late, other), sound splashing around, convolution or some other kind of nice sounding reverb, and it's mostly that reverb tail and splash that gives my mixes a sense of space.

I don't worry about "too much or too little EQ".  Instead I think, "That sounds too [harsh, sibilant], cut it", or "that part of the song feels important to me, I can't hear it, boost it".

Then I try to think, what feels wrong, and fix it.  The name I give it may be air or clarity but in the end it's just a vague hunch.

I am not a professional here, but I have spent a lot of hours listening to pros talk on Youtube about mixing, and it seems to me that in the end, we're not putting people on mars here, we're tweaking EQ knobs and saturators, and limiters and whatnot.  IN the end, we're making music, and as such, we're the kings of overthinking everything.

I think I could add "more air" with EQ, or take it away, I could add "more air" with reverb, or dial back the reverb and make a space feel dry, and yet still some day come up with the opinion that somehow that "added more air" to the mix, meaning almost the reverse, that I feel my song gets over to the listener better.  Who knows what everyone else means when they say "more air".

Warren

[Ted]

Things get easier as soon as you accept that: everything affects everything!

(Not trying to sound Zen btw...).

That's the butterfly effect – chaos theory.

... in the end, we're not putting people on mars here, we're tweaking EQ knobs and saturators, and limiters and whatnot.  IN the end, we're making music, and as such, we're the kings of overthinking everything.

I think only some of us are cursed with overthinking everything. In the last week or more, I've spent a lot of time on my computer analyzing music, and also thinking about how to arrange my pedal board when my new gear arrives. I could have just been playing and experimenting and seeing what kind of magic happens.

Going to do some of that right now.

[StephenM]

I actually read all this and wrote a long reply and then deleted it... it's at least somewhat interesting this topic!