COSM Revisited - A Fresh Look at the Amazing Modeling Technology Inside BOSS and Roland Guitar Products

Let’s Get Physical

COSM is actually an amalgamation of many different digital modeling technologies developed by BOSS and Roland. These were created to precisely model the electronic, mechanical, and magnetic characteristics inherent to an instrument, amplifier, or speaker, and also to create completely new sounds. In concept, the COSM process is not unlike the amazing computer-generated imagery (CGI) we all see in today’s high-tech films, where complex software is used to digitally construct people and animals from the inside out, from skeleton to muscles to skin.

COSM models all aspects of an amp’s circuitry—every component, every path.

Variable Guitar Modeling, or VGM, is the main component of COSM when it comes to guitars and basses. It can be broken down into three separate elements:

• Electronic modeling—With this process, BOSS and Roland engineers analyze and simulate the actual electronic circuitry and how it interacts in a device such as a vintage guitar amp or a classic stompbox. This includes the detailed behavioral characteristics of vacuum tubes, transistors, and all other electronic components.
• Magnetic modeling—Electromagnetic components are a huge part of the sound of electric guitars and amps; this VGM process simulates the characteristics of guitar pickups, amp transformers, speakers, and more.
• Physical modeling—This process is a central part of COSM instrument modeling. It simulates the characteristics of the materials used to construct an instrument, including the type of wood, the metal parts, and even the finish. Physical modeling is also used to analyze the construction materials used in different guitar speaker cabinets.

Measuring sound in an anechoic chamber.

Harmonic Restructure Modeling (HRM) is another component found in some COSM guitar products. The vibration of a guitar string generates many harmonics, and these harmonics define the actual sound character of guitar sounds as we recognize them. With HRM, BOSS and Roland engineers manipulate these harmonics and change them to create very un-guitar-like tones, while still retaining feel and playability of the guitar. In a Roland V-Guitar System, for example, HRM applies the harmonic characteristics of organs, reed instruments, and synths directly to your actual guitar.
When all the VRM and/or HRM elements are brought together, the result is a realistic composite of the individual components of the object whose sound is being modeled. That’s a real mouthful, so COSM’s extended name describes this process much more elegantly: Composite Object Sound Modeling. Get it?

Realtime, All the Time

COSM accomplishes all its modeling magic in real time using super-fast digital signal processing to alter the guitar’s sound as you play. Your guitar’s string signals are the fundamental building blocks of the sound you hear, even when the real-time modeling process modifies that sound into something quite unlike a guitar. As such, COSM retains the natural feel and responsiveness of your guitar playing, with every subtle, expressive nuance coming through.

source:   http://www.bossus.com/boss_users_group/article.php?ArticleId=1319