Weather Got Your Instrument a Little Wolf-ey?

In the classical music world, you often hear the term “wolf tone” or “wolf note” floating around. It’s no secret to string players. Many deal with it. But the editorial team at CIM wasn’t quite sure exactly what it was, and we began to ask around. At first we got a lot of the same responses: “Yes, my instrument has a wolf. Sure, I can play around it. No, I don’t know where it comes from or what causes it.” Thus, our quest to find out began.

WHAT IS IT?

First, let’s clarify what a wolf is. Nontechnically (we’ll get technical later), a wolf is a note played on a stringed instrument that doesn’t have the same clear beautiful tone, or projection as other notes. It occurs most often in cellos and violas but can plague all stringed instruments. “It sounds like the sound is somewhat distorted, and it can cause the pitch to waver slightly,” says Jeffrey Irvine, co-head of the viola department. “It can also come out as a scratchy sound.”

“You’ll be playing along, and all of a sudden it will sound a little like ponticello, which is the effect of playing the string right next to the bridge,” says viola faculty and Cleveland Orchestra member Mark Jackobs. “It gets kind of glassy. I have no idea why it’s called a wolf tone. It just kind of sounds like it’s missing all of a sudden. Or it might squeak a little bit.” The issue is within the instrument itself, and the player is not to blame; however, having a wolf doesn’t mean that the instrument is of bad quality. “I just played on a Goffriller viola from a dealer friend of mine,” says Jackobs. “It’s a million-dollar viola. And it had one. It was barely there because it was set up so well, and it’s such a great instrument. But it doesn’t matter—a hundred bucks or a million bucks.”

Cellists deal with the acoustical oddity the most. “It’s one of those notes that has a really hard time speaking,” says freshman and cellist Daniel Kaler. “I have usually found it to be on the G and C strings.” So, we’ve got a note that doesn’t speak, found generally in stringed instruments with a lower register. Now we’re getting somewhere. 

TAMING THE WOLF

If some of the best instruments in the world have a wolf, why don’t we (the non-musicians) ever notice it? It turns out there are a lot of things you can do to help diminish a wolf. There are wolf eliminators, which are little devices you add to one of the strings behind the bridge or glue to the body of the instrument, most commonly used by cellists. Kaler has used wolf eliminators, but he wasn’t happy with the result. “I felt it was restricting my sound a little bit on other strings,” he says. “It’s a nice tool, but I think that the cost of the sound on the other strings might not always be worth it.” Instead, he pushes the instrument more with his knees when he encounters that note. “It restricts some of the vibrations of the wood, which in turn contribute to producing the wolf tone,” he says.

You can play around a wolf by playing the same note on another string. You can also adjust things like bow pressure and bow speed and make changes to the instrument itself. “There’s an enormous amount you can do with sound post adjustment and with the strings—changing the tension on the instrument,” says Jackobs. “Everything that goes into playing, even bridge angles and bridge height.” However, these techniques won’t completely fix the problem. “It’s something you can control to a certain extent,” says Irvine. “But there’s a certain part that you can’t control. If it’s only a weak wolf, and if the player controls it well, the audience may not even be aware of it.”

A WOLF IN THE MAKING

We spoke to luthier Hiroshi Iizuka, the maker of Irvine’s viola, who shed some light on how to avoid building a wolf into an instrument. The key, it seems, is in the thickness of certain parts of the instrument itself. “If the plates or the ribs are made too thin, the body over-vibrates,” says Iizuka. “But the ribs have to be thick enough to make the body stable. As a maker you must control this.” Iizuka went on to explain that there’s a balance of thin and thick that must be struck for a quality instrument. “A factory-made instrument is very thick, and it doesn’t have wolf tones, but it also isn’t a very good instrument.”

Iizuka explained that a maker or restorer could glue extra wood or even cloth to add thickness to the ribs or plate of an older instrument to make the instrument less sensitive. Other solutions include making the sound post thicker—although Iizuka doesn’t think this is particularly effective—adding a heavier tailpiece, or a heavier bridge. But in the end he admits that every instrument is different. And by the sound of it, there seem to be hundreds of minor adjustments to about every part of the instrument to help eliminate this unpleasant note.

NOW WE’RE GETTING TECHNICAL

It’s safe to say that most musicians who play stringed instruments know about this issue, especially violists and cellists. But the science behind it remains largely unknown to even the musicians who deal with it on a daily basis. “We couldn’t all give you the physical explanation of it, but we know a wolf is there on some instruments,” says Irvine. Most musicians we polled say they’ve always been aware of the issue—what it sounds like and what to do to avoid it. What we needed to find out next was, why?

After checking out a tome from the library filled with dizzying formulas, diagrams and symbols we’ve never seen before, we found Dr. Robert Celmer, director of the Acoustics Program & Laboratory at the University of Hartford, who helped us understand the problem. Mercifully, he took it slow. “First, the wooden bodies (soundboards) and cavities of the violin, viola, cello, etc. are very important to help make the instrument audible,” he explains. “If you’ve ever strummed an electric guitar without plugging it in, you hear how quiet it is. That’s because the string doesn’t have much surface area and thus can’t move a lot of air. You can’t cool yourself off by waving a noodle in front of your face, right?!” Thank you, Dr. Celmer; you’re speaking our language.

He continued. “Thus, the wood and the cavity within actually vibrate at the same ‘notes’ played by the string (called resonance), and the larger surface area of the soundboard pushes much more air and gives the instrument its full sound character and helps it project into a concert hall.” Got it. Cavity plus surface area equals projection.

“Second, have you ever tied one end of a rope to a garage door handle and shook the string up and down to create ‘standing waves’ on the string? When a cello is bowed, the string is set into vibration, and those waves travel down the string to the bridge, which is the effective ‘end’ of the string at that end. Normally, the bridge acts as a solid object (like the garage door) and causes the waves to reflect back down the string, creating the same type of standing wave pattern.” OK, we’re still with you.

“However, at certain notes played on the instrument, one of the body resonances is especially strong, which causes the bridge to no longer act like a solid wall, but instead moves quite significantly due to the body’s resonant motion.” In other words, when the vibrations are too strong, the bridge wobbles.

“When this happens, the bridge loses its ability to reflect the energy back down the string, and thus the player loses the feedback of the string vibration so crucial during the bowing motion.” So essentially, the bridge is no longer the sturdy garage door. “The result is that the overall sound level drops, which in turn causes the body resonance to die off, at which point the bridge becomes rigid again, and reflections off the bridge begin to reestablish themselves. This creates an endless cycle of the instrument rapidly growing and dropping in sound level at about five times a second. This condition makes it virtually impossible for a player to produce a steady sound. The note being played when this phenomenon happens is called a ‘wolf note.’”

Eureka! In sum, when the resonance is too strong, the vibrations make the bridge unstable. When it’s unstable it can’t adequately bounce the soundwaves back, causing the sound to drop. When the sound drops, the vibrations die down as well, stabilizing the bridge once again, allowing for projection once again. This in turn results in too much vibration, thus continuing the vicious cycle.

There you have it. The wolf fully explained—to both those who’ve never heard of it and the musicians who know it all too well. Now, can anyone tell us how it got that name?

This story was originally published in the winter 2016 Issue of Notes magazine.