What we found was actually obvious: the biggest variation in tonal balance can be roughly categorized by the intended listening environment. Music that you might listen to in a symphony hall, e.g, classical/orchestral, tends to have its spectral balance dominated by mid-range frequency bands. Music that you might listen to in a club, e.g., hip-hop or certain kinds of electronic music is extremely bass heavy, and most other modern popular music typically enjoyed over headphones or home stereos is somewhere between these two extremes. We then analyzed the variation over all the tracks in each of the “Modern,” “Bass Heavy,” and “Orchestral” groups in order to provide targets quantifying the tonal balance “typical” of best practice norms.
Creating Your Own Guides
Although the three targets provided with Tonal Balance Control provide rough guidelines of the typical best practices in modern recording, many well-balanced tracks might be outside of these bounds some of the time (during a saxophone solo) or even most of the time (a reggae death-metal polka track). It’s also typical in many mixing and mastering workflows to use a reference track (or tracks) to help craft your sound. For this reason, you also have the option in Tonal Balance Control of creating your own target from a single audio file, or creating a composite target from a folder of files, providing the ability to define your own “genre” targets.
As previously mentioned, the Modern, Bass Heavy, and Orchestral target curves included in Tonal Balance Control were created from thousands of tracks. Thus, creating a comparable target from only a single file represented a bit of a technical challenge. Ultimately, the solution we settled on treats every second of audio in a similar way to an entire track in our large-scale analysis. While these custom target curves can be extremely effective, because they are created on such small amounts of audio, things like a mellow intro, drum solo, breakdown, etc. can potentially have a large impact on the calculated targets. Therefore, if you really are trying to closely match a particular section in a highly variable track (e.g., “Bohemian Rhapsody”), you might want to isolate that section in an audio editor before creating the target curve.
Displaying Tonal Balance
In deciding how to display our target curves with a “zoomed out” spectrum analyzer, our goal was to develop a way to quantify whether a given spectrum was tonally balanced with respect to a target. To achieve this, we went back to the “poorly balanced” mixes in our dataset and tried to understand what separated them from “well balanced” mixes. Comparing the entire spectra didn’t turn out to be very useful, but by grouping the spectra into regions and then comparing those regions to the target, all of the poorly balanced mixes were very different from the well balanced mixes in at least one frequency area. Inspired by the way Bob Katz divides the frequency spectrum in the Carnegie frequency chart from his book Mastering Audio: The Art and Science, we divided the spectra into four regions: (1) Bass, below 250 Hz, (2) Lower Midrange, 250Hz -2 kHz, (3) Upper Midrange, 2-8 kHz, and (4) Treble, above 8 kHz.
The “Broad” view in Tonal Balance Control displays a spectrum analyzer, but with all information condensed into the four frequency regions mentioned above, and the target displays the typical variation expected in each frequency range. This view is extremely useful as a “gut check,” to make sure your mix has no glaring tonal balance issues, however, you shouldn’t be alarmed if you are occasionally outside the targets during intros, outros, solos, etc. If your mix does not appear well-balanced in “Broad” view, we also provide a “Fine” view, which displays a more typical spectrum analyzer view (although things have been level normalized and smoothed in time and frequency to still maintain the zoomed out tonal balance qualities). Fine view can be very useful in deciding where exactly to make an EQ change to better match your target frequency spectrum, and using iZotope’s new cross communication technology, you can control any Ozone or Neutron EQ anywhere in your session without leaving Tonal Balance Control.