Timbre and Harmonic Distortion

Let’s look at the relationship of timbre to distortion, because the two are cousins if not siblings. We’ll also compare clipping to compression, differentiate the sound of the two, and get that firmly in your ear.

Four or Five Characteristics

Sounds have four main characteristics: pitch, timbre, loudness, and envelope. And duration, but we don't need that right now.

Pitch we know about. Loudness we know about.

Timbre is a mix of pitch and loudness. All instruments—indeed, all objects, have a timbre when you give them a good klonk or whatever it is that needs to be done to get the thing to make noise. Ping a glass with your fingernail and there is a distinctive "glass" sort of sound. Get two of the same glasses, ping them both and you'll notice that they don't sound exactly the same. This is because each glass has a slightly different overtone series—a slightly different set of harmonics, which are frequencies above the loudest frequency, the fundamental, that gives the note its pitch name.

The overtone series of every instrument is different. We call a sound with a lot of high overtones "bright," with lower overtones "warm." Depending on the math of it all, overtones can also make things sound harsh or smooth, or even in or out of tune. I wrote more in-depth on this stuff here.

Timbre is Overtones

So, you have a note at 329.63 Hz, and you'd like to make it brighter, so you put an EQ on it and turn it up, but you don't have the frequency of the EQ at 329.63 Hz, do you? You have it at like 8kHz or something. A shelf at 15kHz. That EQ is turning up the overtones of the note, right? It gets brighter because you're amplifying the overtones.

For some of you, this is "Duh." For others of you, this is, "Oh really...? Hmmmm..."

What if, instead of amplifying the overtones of an instrument, we added more overtones into the picture? We generated some additional overtones that are consonant and harmonious with the fundamental, and added them into the sound. It would be brighter, right? It would be subtle, not as noticeable as an EQ boost, but it would make an audible difference.

That, campers, is what happens when you drive a signal into tape or a circuit a little too hard and start clipping it. It generates additional overtones—harmonic distortion. This is what happens when you saturate tape, or saturate a transformer, or overload a circuit on a preamp. Heck, just passing a signal through a compressor with no compression happening causes some additional harmonic distortion to happen, which changes the timbre of the signal. This is what people are talking about when they say, "I'm adding this not for the compression, but for the color."

Instruments sound the way they sound in part because of their timbre. Equipment sounds the way it sounds in part because of its harmonic distortion. These are the same thing, really.

Timbre and Harmonic Distortion Fall in Love at an All-Inclusive Resort

So, some instruments naturally sound better with some pieces of gear because the timbre and the harmonic distortion are complementary. And things can also sound bad because of the relationship of these two things. I found out pretty early in my career when I was recording guitars through distorted amps, that sometimes, if I doubled a part with two different amps, it might actually sound a little thinner when mixed together, or buzzy and harsh, and in some cases, out of tune. It was overtones and the timbres not lining up.

It's dumb luck that the harmonic distortion caused by tape compression/saturation generally enhances the tonality of most instruments. Same thing for circuits using tubes. The same thing for transformers. Rather than EQing a vocal to get it to sit better, we can smush it a little bit into tape and it gains a bit of presence and "bite." We can get a bass or a kick to have more authority on small speakers by pushing it a little bit harder through some transformers, which tend to generate harmonic distortion that is lower in frequency than most of the stuff generated by compression/saturation/distortion.

Slamming cymbals through things often sounds like ass—really nippy and harsh. Too much harmonic activity. Higher voices and higher-pitched keyboard parts can get really nasty with too much extra harmonics up there. Danger Will Robinson!

Don't forget, ALL analog gear and all ANALOG MODELED digital audio adds some harmonic distortion, and things change timbre due to this as levels go up and down. At Korneff, we spend MONTHS on the modeling to get all the distortion and harmonics behaving in an authentic, analog way. It's easy to make a plug-in that does something. Relatively speaking. It isn't as easy as, oh, making toast. But it's much more difficult to make a plug-in that really captures the analog inspiration.

Harmonic distortion ain't the only thing that happens when you club a baby seal of an audio signal with a 600 pound tape deck. Or a feather-light Echoleffe Tape Delay. You also change the waveform.

Clipping Made Easy

Any sound has an envelope. This is how the sound varies in loudness or power on a micro level. My easy way to think of it: there's a distance between the loudest bit of the sound, usually the attack, but not always, and the quieter bits of the sound—the way the note dies off, the resonances of the body of the instrument (or of a speaker cabinet or a room). The little rattles and noises and squeaks things make.

Compression changes the distance between the loud bit and the quiet bit.

Tape compression and saturation squash the signal (compress it) with an immediate, instantaneous attack that definitely clips the transient a bit. This is true of ANY signal that you slam into clipping: you lose some attack. But saturation has a very very fast release. Like, slightly less than instantaneous. Actually, for our purposes, it's instantaneous.

So, when you squash something into tape, not only do you add harmonics, you lop off the loud bits and smush them down, and because you're increasing the level to do the smushing, you're also bringing up the quiet stuff.

Back to our snare. If we smash it into tape, it gets a little bit THICKER, because we're adding harmonics, and a little bit LONGER ACROSS TIME, because we're changing the relationship between the loud and the quiet. You understand that if we bring up the quiet stuff, the sound will appear to last longer, right?

And you realize that lengthening a snare will change the groove, right? It will sound more "behind the beat" if you squash it into tape.

Now, crushing guitars into tape adds a very nice set of overtones that give them a little more brightness, but the transients are getting slightly clipped, and they get a little bit less distinct and less punchy. You lose the "click" of things. Same thing with pianos or any sound with a fast attack. Slam it into tape or a tube or a preamp, clipping it, and you'll lose that transient a bit. Same with vocals. When I was recording rap stuff, I would cut the vocals a little bit lower so as to not lose articulation and wind up with it sounding mumbly. I would cut punk vocals clipping into tape to deliberately get them a little less articulate and at the same time bring up the spittiness and the mouth noises (that's quiet stuff) so the whole thing sounded more "in yer face."

If you think about it, if someone was in your face screaming at you, you'd hear all the mouth noises. You might even taste the mouth noises.

Homework

So, set up a mix. Route everything to a stereo subgroup. Label this CLEAN. Add two pre-fader sends from this and send each to a different stereo subgroup.

Put the Echoleffe on one subgroup and set it to Tape Emulation mode. This is the group that's going to clip everything using tape saturation. Label this one CLIP. Everything going through this will lose transients but gain harmonics and gain length (the quiet stuff will get louder).

Put the Pawn Shop Comp on the other subgroup. You can use the default setting. Set the ratio to like 6:1 and drop the threshold until the meter is bouncing musically. We want to compress, not limit. This compressor will bring out the transients and push down the quiet stuff a bit. Label this COMPRESS.

Route all three subgroups—the clean, the clip and the compress, to your stereo master.

How does it sound with all three up? How does it sound if you pull down CLEAN all the way? Did you set the sends to pre-fader? If you didn’t, you're about to find out why they need to be set that way.

Throw a LUFS meter on it and mess around with things. Can you get something like a -8 LUFS-S reading without it sounding like utter ass? And without driving things over like -1dB true peak?

Play some more. Maybe route some sounds just to the clip, and others just to the COMPRESS. What works best where?

By the way, if you don't know, what you're doing is parallel compression and parallel saturation. I know most of you know this, but there are a lot of beginners reading this, too.

You will learn tons if you do this.