Working with Tension: The Excitator

Tension defaults

Oh Tension, how I hate you and despise you. You are the most mysterious device Ableton Live has to offer, yet one of the most interesting and powerful. If only I could coax you into doing my bidding, I would have a wonderful addition to my arsenal of synthesis…

If that’s what you think every time you see Tension at the bottom of the list of Live Suite instruments, then this series is for you. I’m in your boat — not really sure how Tension works, just using it to get cool sounds by playing with knobs. So I’m going to do the dirty work of digging through the Ableton documentation, figuring out what each of those knobs do, and (hopefully) demystify this confusing device.

Here’s the roadmap:

  • Part 1 (this article): An introduction to Tension and the Excitator
  • Part 2: The String
  • Part 3: Damper, Termination, and Vibrato
  • Part 4: Pickup, Body, and the Filter/Global Panel
  • Part 5: Using Tension to make amazing sounds

Each article will provide information about Tension, and finish with a homework assignment. Hands-on practice is extremely important in building familiarity with an instrument, and Live’s devices are no different! Who knows, if you make something awesome, you can submit it to us and sell it in the AbletonOp Store!

Aaaaannnd…let’s get started!

A Blank Slate

Here’s what the default Tension template sounds like. I’ve added just a bit of reverb to make it sound a little more alive:

The mesmerizing attack and sudden, subtle decay of this default string patch makes it an amazing sound to start with — at least far more interesting than the sine wave of Operator. It’s a good starting place, but something that can definitely be improved.

An Overview of Tension

Tension attempts to mathematically create a physical model of string instruments, and is organized in a mostly intuitive manner, as long as you keep that goal in mind. The main sections of Tension and their functions:

  • The Excitator is what touches the string. This can either be a Plectrum (like a guitar pick), a Hammer (like on a piano or dulcimer), or a Bow (like on a violin). This section of Tension is concerned not with the quality of the string, but the quality of the object making the string vibrate.
  • The String is the vibrating part of the instrument. This part of Tension models its behavior, such as how long it vibrates, the amount of high frequency damping, etc.
  • The Vibrato simulates vibrato. If you watch a concert violinist play, when holding long notes, he will wiggle his finger back and forth, changing the pitch of the string slightly. Live uses an LFO to simulate this.
  • The Damper simulates muting of the string. In the real world, this is when you release a key on a piano, or when a guitarist touches the strings on the fretboard without pushing them down fully.
  • The Termination determines how the model of the finger interacts with the model of the string and the fret, by effecting parameters like fret stiffness and the force with which the finger is applied to the string.
  • The Pickup controls where a pickup (like on an electric guitar) is positioned, and if it is enabled.
  • The Body is the larger instrument holding the string. Depending on the size and shape of the instrument (upright vs. grand piano, violin vs. cello, etc.) the instrument will sound very different. Live models this mostly through preset models, but there are four extra macros to introduce a little bit of customization.
  • The Filter/Global tab should look fairly familiar, so I won’t cover it here. It will be covered in depth in Part 3.

We’ll just be covering the Excitator in this article, which alone amount to a ton of different and unique sounds.

The Excitator

This is, arguably, the most important part of Tension. The sound of an instrument depends very much on what you hit it with, and the complexity and variability of this interaction is reflected in the amount of controls Ableton supplies you with in this section. It’s the most complicated part of Tension, and rightly so. The sound starts here, and it’d better start juuuust right. But at first glance, this can be a confusing interface. Let’s demystify it by going over the three excitators in turn:

PLECTRUM simulates a picked or plucked string. Its parameters are:

  • Protrusion – the amount of the plectrum’s surface placed under the string. Little protrusion means you are barely plucking the string, the result being a soft and thin sound.
  • Stiffness – how stiff the plectrum is. Think of this as a hard pick vs. a light thin pick. This affects the volume and thickness of the sound as well.
  • Velocity – how fast the plectrum moves across the string. At very low values, this means that the pick takes a little bit to release the string, resulting in a delayed sound. At high values, the pick plucks the string extremely fast, resulting in a very loud sound.
  • Position – the position where the plectrum strikes the string. 0% is the string’s “termination point” (Like playing a guitar very near the bridge). 50% is the midpoint of the string, which results in a deeper sound. Assuming the string is symmetrical, any position above 50% wouldn’t affect the sound, it would just be mirroring the first half of the string (i.e. 20% = 80%, 30% = 70%, etc.). These amounts are relative to the string length, though — as in a piano, where the hammers strike the strings at different points depending on the length of the string. However, on a guitar, the pluck position is usually in the same area. To simulate a guitar correctly, then, the Fix. Pos. button must be enabled.
  • Damping – how much of the force of the plectrum on the string is absorbed back into the plectrum. This models the sort of spring force of the hand moving the plectrum. Higher damping values give a loud and bright sound, because the “spring” motion of the hand is going to be more extreme.

BOW simulates a bow, as on a violin or a cello. Its parameters are:

  • Force – the pressure with which the bow is applied to the string. Less force will give you softer, sweeter sounds, and high force will give you distorted, scratchy sounds.
  • Friction – the friction between the bow and the string. This has a lot of bearing on the sound of the string, especially when the force being applied is more delicate (lower value). Be careful with low force values and high friction values — if there is too much friction and not enough force, there will be very little sustained sound, and you will only hear an attack.
  • Velocity – the speed of the bow across the string. Make sure to adjust this carefully; the “best” velocity value will give you a considerably richer sound, while moving the bow too fast or too slow results in either a distorted or out of tune, tinny sound.
  • Position – same as the Plectrum

HAMMER simulates a hammer, as on a piano. Its parameters are:

  • Mass – the mass of the hammer. A low mass gives a thin sound, and a high mass gives a loud attack.
  • Stiffness, Velocity, Position, and Damping work basically the same as the Plectrum

The Hammer (bouncing) excitator is very similar to the hammer, by nature, but instead of being below the string and pushed up, like on a piano, it is dropped from above the string. With the right parameters, you can get a bouncing effect, as is heard on a hammered dulcimer. Here’s a video of Arlen Oleson, a dulcimer player who plays in New York City’s Central Park. I had the pleasure of watching him for a good hour when I was there a few years ago:

To see a great example of the bouncing hammer in Tension, open up the preset Plucked-Chord Bouncing, which is found under Instruments → Tension → Guitars and Plucked. Because the Mass and Velocity parameters are modified by the MIDI velocity, if you don’t hit the notes on your MIDI keyboard hard enough, you won’t get any bounce.

Use the Excitator Carefully

Below these parameters, you can see the velocity and key sensitivity for each one. This allows you to delicately affect the parameters depending on MIDI note value and velocity, which is an awesome tool for creating rich and expressive sounds. Make sure to take the playability or expressiveness of your sound into careful consideration before declaring it finished!

The most important thing about Tension’s excitator is subtlety. Move the knobs slowly, and play with them easily. I highly recommend mapping all the macros to knobs on your MIDI controller so you can immerse yourself in the instrument and forget that you’re using a computer. It takes a lot of precision to get the right sound in Tension — more so than in Operator or Analog, in my opinion. Using those synthesizers, you can be a bit more coarse in your decisions and still come up with something decent.

One last tip to leave you with: Always keep in mind the physical instrument you are modeling when playing with these parameters. Picture a guitar or violin in your head if you’re trying to simulate these sounds. Unlike other types of synthesis, physical modeling can be very intuitive as it is based on familiar objects (such as strings, bows, and hammers) rather than abstract mathematical entities. While Tension does look a bit daunting and confusing, and can often surprise you, as long as you’re always considering the physical model, you should be able to target the sound you want and achieve it.

Homework!

Yep, that’s right, you’ve got homework. If you want it, at least. :)

I want to hear what you guys can do with the excitators. Your assignment: Modifying just the excitator section, and using Live’s built-in effects, make a Tension patch that models a surreal instrument. In other words, take a common existing sound (like a guitar) and turn it into something crazy (like a guitar made out of glass). Email them to [abletonop] at [gmail]. I’ll showcase my favorites for the next article on Tension.

Also, what is your experience with Tension? Most of the Live users I talk to seem to ignore it, which is one of the reasons I’m writing this article. Let us know in the comments!

Next, check out part two →

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