Tech Tip: EQ Curves and Musical Style

Do certain styles of music have a "signature" EQ response? Check out the following curves, and decide for yourself.

By Craig Anderton

Look  at music with a spectrum analyzer, and you might be surprised at what  you see. For example, if you analyze a bunch of music that belongs to  the same musical genre, you'll start to detect a pattern with respect to  how energy is distributed over the frequency spectrum. Granted, it's  impossible to generalize for all types of music within a genre, but  there are often recurring similarities that can be pretty interesting.

The curves shown in this article were researched by Har-Bal (www.har-bal.com)  who make EQ-oriented mastering software. Har-Bal is not a  “curve-stealing” program (like Steinberg's FreeFilter or Voxengo's Curve  EQ) that impresses the spectrum of one song onto another, but allows  displaying “reference curves” if you like a particular sound, and want  to see how your master differs from it.

In  the process of developing Har-Bal, the company thought it would be  helpful to include typical frequency response reference curves for  different types of music. Analyzing them yields some interesting clues  about EQ's relationship to style; in all of the following examples, the  upper (yellow) curve shows peak power, and the lower (red) curve shows  mean power.

Dance/Techno

In  Fig. 1, the hyped low end around 80Hz corresponds to the strong kick  and bass line. There's a slight dip at 5kHz, but then the response  climbs up again in the treble range to give presence and sizzle. This  results from the accented high-hat and percussion parts, which help  propel a song's rhythm and is a crucial element of dance music.

The  rest of the curve is relative flat, where all frequencies are  emphasized. The object is to produce loud, pounding music that gets  people moving on the dance floor, and that's what this curve indicates.

Fig.  1: Here's the spectral response curve for a typical techno song. Note  the “bump” around 80Hz, which indicates a strong kick drum and bass.

Classical

The  most distinctive characteristic here is the rapid rolloff in the treble  range (Fig. 2), as you'd expect from acoustic instruments and a sound  that doesn't include thrashing symbols, synths with huge amounts of  harmonics, or boosted treble for radio play. The bass bump may be a bit  surprising at first, but orchestral bass drums, tympani, and double-bass  contribute a lot of energy to the final sound.

Fig.  2: Classical music typically adds very little processing (either EQ or  dynamics), which results in a lower amount of high-end energy.

Rock

Fig.  3 displays the strong bass typical of rock music, but note there's also  a lot of midrange action in the 500Hz-3kHz region from guitars, vocals,  leads, and so on. The highs aren't quite as hyped as the techno curve  because there aren't as many electronic instruments, although cymbals  and distorted guitars can add a fair amount of high-frequency energy. As  a result, there's a more natural rolloff that resembles the classical  curve, but with more high frequencies.

Fig. 3: Rock music tends to have a lot of energy in the midrange region.

R&B/Hip-Hop

Like  rock music, Fig. 4 shows there's a significant midrange emphasis due to  vocals and instruments such as guitar, piano, synth, etc. But also note  that there's definitely more bass (check out the energy in the kick and  bass guitar/synth bass range), as well as a bit more high-energy  action. The lower mids around 200-300Hz are down a bit; this generally  produces a cleaner, less “muddy” sound that's indeed characteristic of a  lot of R&B and hip-hop.

Fig. 4. The R&B/hip-hop curve is similar to rock, but with more lows and highs, and a bit of a dip in the lower midrange.

Folk

The  curve in Fig. 5 is for an acoustic folk ensemble. As befits acoustic  music without significant amounts of drums or bass, the accent here is  on vocals, guitar, and other midrange instruments. Bass and treble both  fall off substantially; unlike classical music, you don't have powerful  instruments in the bass range (like tympani) to contribute large amounts  of low-end response.

Fig.  5: The curve for folk music is quite similar to classical, which is to  be expected as both forms of music favor acoustic instruments.

Adult Contemporary

This  is also called “new age” music or easy listening. This type of music is  designed to accent melody and not produce sizzling highs or pounding  basses, which Fig. 6 clearly indicates: There's a significant amount of  midrange energy, and a gentle tapering in the bass and treble regions.  However, note there is a bit of a peak around 7-8kHz. This is  characteristic of tunes that include bright percussion, like shaker,  tambourine, maracas, and the like.

Fig.  6: Although the highs and lows taper off somewhat as with acoustic  music, note the high-frequency “bump” characteristic of percussion

So What Does It All Mean?

These  graphs are designed to illustrate some points about spectral  distribution is certain types of music, not serve as a “rule” about how  music should sound. Still, as you're mixing, it's useful to know the  characteristics of other music in the same genre, so your song can slide  relatively easily into a playlist. For example, if you're mixing dance  music and you don't have a prominent kick and some high-end sizzle, the  music will sound weak when compared to other dance music.

As  always, your ears need to be the final arbiters of what sounds correct.  But given the importance of EQ in producing a finished master recording  with a commercial sound, the more you know about what you're doing, the  better!