Modulation Monday – Under Pressure

Published by john worthington on

One of the things that makes Jambé unique is that its sampler-based synthesizer is based around continuous pressure data from its pads. Unlike most MIDI percussion controllers, that pressure is available for modulation at all times. In this post, we’re going to explore the ways you can use pad pressure as a modulation source.


But first we should talk about pressure in general and pad calibration. Jambé measures the pressure on each of its 10 pads 1,000 times a second and converts that reading into a value between 0 and 1023. To keep things simple, the sound engine always thinks of pressure as a value in that range. But what if your personal playing style doesn’t cover that whole range? Calibration lets you configure Jambé so your softest and hardest hits get mapped to Jambé’s full pressure range. Some of us naturally hit softer than others. Some hit harder. Playing with your fingers is going to produce different pressure data than bashing with sticks. Getting familiar with the Calibration Editor will let you customize Jambé to your personal performance style. 

Just under the main segmented control, you’ll find the Kit drop down menu. This menu allows you to access the various kits without returning to the Play Screen. It also has some commonly used functions. 

At the bottom of the list of commonly used functions, you’ll find the “Calibrate Pads…” option. Tap it and you’ll get the Calibration Editor.

In the Jambé app, we refer to Jambé pads by number. Here’s a quick reference of how the pad numbers map to the pads on a Jambé.

There’s a row in the Calibration Editor for each pad. The “Lo” and “Hi” values are the current calibration settings. The default for “Lo” is 25. The default for “Hi” is 941, which is probably what you see when the Calibration Editor comes up for the first time. Raw pressure values less than or equal to the “Lo” get set to 0. Any value 25 or less in this instance. Values greater than or equal to the “HI” get set to 1023. Raw values 941 or higher in this case. Raw pressures in-between get intelligently scaled between 0 and 1023.

The “Live” column shows you the current pressure coming from the pad. We show the highest value received. The “Copy to All” button will copy the “Live” value from that row to all of the other rows. This is convenient if you want to calibrate all the pads the same.

The last column, “Calib”, shows what the calibrated value of the current “Live” value is. This is the calibrated pressure value the Jambé app works from. In the screenshot above, you see a “0” in the “Calib” column above because all of the “Live” values are less than the “Lo” value of 25.

At the bottom of the editor are the action buttons:

“Enable Live” enables the update of the “Live” value.

“Reset Live” resets all of the Live values. if “Enable Live” is set, they’ll start updating immediately.

“Live->Lo” copies the “Live” value for each row into the “Lo” value.

“Live->Hi” copies the “Live” value for each row into the “Hi” value.

“Revert” reverts “Lo” and “Hi” to their previous values.

“Default” restores “Lo” and “Hi” to their default values.

“Max” sets “Lo” and “Hi” to 0 and 1023.

Putting all of this together, the typical calibration process would look something like this:

1.) Hit a pad as softly as possible.
2.) Tap “Copy to All”
3.) Tap “Live->Lo”
4.) Hit a pad as hard as possible.
5.) Tap “Copy to All”
6.) “Tap “Live->Hi”

If you want to calibrate the pads individually, skip the “Copy to All” steps and work through each pad. This can make a big difference if you tend to play some pads with sticks and some with fingers. If you’d rather enter a value directly instead of hitting a pad, you can tap “Lo” and “Hi”.

Why are the defaults 25 and 941? During our development, we found those defaults worked well for most players. If your “Lo” value is lower than the “Live” value with no pressure on the pad, you may get false hits. 25 has been a pretty safe number across all of our testing. We’ve noticed that some of the powered USB adapters for iPad can be electrically noisy. This means you might see higher “Live” values than expected, even when there’s no pressure on the pad. If you’re getting false hits, check the Calibration Editor and adjust the “Lo” value accordingly. We’ve had fewer problems with Apple’s adapters.

The calibration settings are stored in the Jambé app’s preferences and not the Jambé hardware. This is handy if you’re sitting in on someone else’s Jambé. Plug in your iPad and you have your kits and calibration ready to go.

Pressure Modulation:

The most common pressure related Mod Source is “Note On Pad Pressure.” The value of this Mod Source gets set to the the pressure that triggered the note. It’s not updated until the pressure on the pad is released at which point it returns to zero. It’s commonly used in conjunction with the Mod Dest “Trim” to scale volume based on how hard the pad was hit. Additionally it works great anytime you want a change in sound that’s based on how hard the hit is. Maybe opening up the filter on harder hits? Or changing the pitch? Just remember that this Mod Source only gets updated when a note is triggered.

Note: I happened to do the screen shots with the Paté kit loaded, but any kit will work. You can download the Paté kit – here.

In the Instrument Editor’s Modulation screen I selected Mod Path 3 and configured it as you see on the right of the screen shot. I set the Max Modulation to 12 semitones (1 octave). When I hit the pad softly, it sounds at the original pitch. When I hit it hard, the pitch goes up. This example is great for showing the concept, but you’ll quickly notice that 1 octave over the entire pressure range of the Jambé isn’t much of a change. Also, Mod Path 2 is adjusting the Trim (volume) at the same time, so the softer hits are not only pitched lower, their volume is lower. Try bypassing Mod Path 2 to hear only the pitch change.

“Note On Cont. Pad Pressure” is very similar. The initial value of the Mod Source is pressure that triggered the note. After that, its value is constantly updated as long as there is pressure on the pad. After the pressure on the pad is released, the value returns to zero. In MIDI terms, you might think of “Note On Pad Pressure” as velocity and “Note On Cont. Pad Pressure” as velocity + after touch. You can try this by changing the Mod Source of the Mod Path we just added from “Note On Pad Pressure” to “Note On Cont. Pad Pressure.” Obviously longer sounds will give you more noticeable results.

The two Mod Sources we’ve talked about so far get their value from the pad you’re hitting and only have a value when a note is playing. You can use the pressure on any pad as a Mod Source as well. This includes the pad you’re hitting. Note that the pad whose pressure you’re using as a Mod Source can also have instruments on it and function normally. “Pad 1 Pressure” through “Pad 10 Pressure” are a submenu of “Pad Pressure” in the Mod Source hierarchical menu.

As an example, let’s add a third Mod Path to the Instrument on Pad 1. I’m using the Paté kit. But pvcWhack will work as well. Go to the Kit Editor and select Pad 1. Then go to the Instrument Editor and tap the Modulation button to bring up the Mod Path Editor. Tap on Mod Path 3 and configure the Mod Path as below. We’re using Pad 2 Pressure to modulate Pitch. The effect is similar to a Talking Drum.

Many old recordings have a special sort of magic because of mic bleed. With musicians playing in the same room, the microphone on one instrument would pick up traces of other instruments. This gave a nice cohesion to the sound. Pad pressure can offer something similar to your kits. On a drum head, if you’re playing fast, the previous hits affect the sound of the current hit because the drum head is already in motion. The sound on the pad you’re hitting can be altered by the residual pressure on the pad you last hit. This can give hits that are close together in time a different character than hits that are completely separate .The possibilities are endless.