MDP Deep Dive

Advanced Tech, Unlimited Expression

“Multi-Dimensional Processing,” or “MDP” for short, is part of all BOSS compact pedals that have names ending with “X”. Bringing together over 40 years of knowledge, today’s advanced processing capabilities, and the company’s powerful development infrastructure, this true breakthrough technology achieves musical expressiveness that’s impossible to realise with conventional effects technologies. In this article, we’ll explore the complex sound production capabilities of the guitar, and how MDP technology works together with these capabilities to bring unmatched creative expression to your music.



Ever since its founding in 1974, BOSS has meticulously researched the sound-making processes of musical instruments, and of guitar in particular. While times have changed and technologies have evolved, the primary goal for this ongoing research has always been simple: to create products that produce the best guitar tones possible.

Among guitarists, the definition of “great tone” is extremely personal, and can vary considerably from player to player. This is because the guitar is such a responsive, interactive instrument that’s capable of nearly unlimited sound variation.

Standard electric guitars can deliver sparkling arpeggios, sweet jazzy tones, bluesy crunch sounds, heavy rock riffs, and many other tones. Extended range guitars with seven and eight strings take things even further. And the sensitive sounds of steel-string and nylon-string acoustics are yet another side of this incredibly versatile instrument.





The guitar’s pitch changes according to what strings are played, and the position at which notes are fingered on the fretboard. If the guitar is equipped with a vibrato bridge (also known as a tremolo bridge), the bridge’s arm can change the pitch as well.

Loudness (Level)

The loudness of the guitar is affected by picking dynamics, and also by the volume control on the instrument. Other factors influence the loudness, including the output characteristics of the guitar’s pickups, the pickup height, string gauge, and more.

Timbre (Overtone Structure)

There are many elements that affect a guitar’s timbre, including its type, brand, material, finish, pickup type and position, and tone controls. These elements are intensified when using effects like distortion. Picking strength also affects timbre, especially when the sound is distorted.

As with all sound, the element of time also comes into play. After a guitar string is picked, the pitch, loudness, and timbre all change in a constantly evolving way as the string vibration decays. This complexity is magnified exponentially when multiple strings are vibrating at once.



There are many additional factors that subtly influence the guitar’s three sound elements, such as pick material, playing with a pick vs. bare fingers, playing the same notes on different strings, and so on. As you play, all these elements interact to produce the guitar’s evolving dynamic response, as shown in Figure 2:

Another important factor is that the overtone structures of low notes and high notes are completely different. And as the sound decays, the volume and timbre of all notes continually change as well. In the case of a distortion sound created by a stompbox, picking harder and physically adjusting the guitar’s volume knob actually has more impact on the timbre than the overall loudness.

This variation in overtone structure is known as “articulation,” and it plays a significant role in musical expressiveness. Simply put, the sense of sound energy is more important than volume level for musical expression.

To illustrate this, imagine the sound of a crash cymbal in a drum set: when the cymbal is struck hard, the sound is always perceived as hard, even if the volume is turned down. Conversely, a soft-struck cymbal is not perceived as a hard sound, even when the volume is turned up.


In the world of guitar, “great tone” is the result of many, many complex elements that interact with each other in a way that’s pleasing to the player. Conventional processing technology is only capable of a one-size-fits-all approach that’s applied to all the elements at once. In many applications, this can provide the best effect. But when the numerous elements vary considerably, the conventional approach can be quite limiting.

For example, you might dial in a distortion to produce tight and even tone that’s perfect for heavy, palm-muted riffs on the low strings. But when you play that same sound on single-note lead phrases in the mid and high ranges, the tone can be thin and sterile. In this case, optimizing your effect for one style reduces the quality of sound for another. And when you adjust the effect to work better for both styles, you end up with a compromise that doesn’t give you the best sound for either.

This is where the powerful MDP approach excels. An MDP distortion analyzes the level, overtone structure, and frequency characteristics—which vary according to picking dynamics, register, string gauge, chord or single note, wound or plain string, etc.—and then continually adjusts itself to apply the best effect at all times. As a result, your distortion is always completely optimized, no matter what style or range you play in.

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