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BEHIND THE SCENES       


This page explains the physical modeling research done by IRCAM in order to bring you BRASS. We hope you enjoy.

  • The Trumpet:
      To characterize the behaviour of the bore of the trumpet, acoustic impedance measurements have been carried out in an anechoic room. This method acts as a precise measure of the echo produced by a trumpet in response to an acoustic impulse: It is in some way as though we shot a rifle in a room in the form of a trumpet or trombone and saved the echo.

In order to characterize and model the interaction with the trumpet player, an artificial mouth device was put to use: this device, equipped with latex lips, was fed in compressed air and really played the trumpet allowing us to reproduce the main gesture controls of a trumpet player.
      The physical model is the ensemble of equations that explain, in mathematical language, the different phenomenon in physics, and are well-understood thanks to the studies of the IRCAM researchers. The fact that the sound produced in BRASS is the solution of equations calculated more than 44,000 times a second attests to their hard work!

      With a physical model the sound is always in evolution. Since the physics of the most up to date studies are included in these equations, the model (and thus the sound) reacts in the same way as the real instrument. The model automatically reproduces the particular sound effects caused by change of fingerings (different valve positions), by the altering of lip tension, by an increase of the blowing pressure and therefore of the sound level (brassy effect) ... Noise induced by turbulence in the air flow is also modelled according to analysis on natural trumpets recordings.

      Playing capabilities of the model are similar to those of the real instrument. However, playing this virtual instrument does not require any long or tedious training; in BRASS you do not need to know how to use breath control or tighten your lips to make a note. In fact, many different values have already been assigned to the control parameters of the model so that notes and playing effects are directly reproduced when playing the virtual instrument through a keyboard.

      The settings of these parameters (or mapping) take advantage of an optimization scheme especially developed within this project. The algorithm starts as a beginner might: it tests thousands of different values, at first randomly, but at its rate of progression, it allows chance to intervene less and less in its training. The algorithm is based on the simulated annealing technique to find optimal values of control parameters so that the model automatically plays the desired notes. You have nothing more to do than to be inspired

  • Trombone:
      The trombone recreation is based on the trumpet model. The main difference, beside the tube dimensions, is that while a trumpeter is limited to a finite number of ways to elongate his instrument (only 8 possible positions) the trombonist has a nearly-infinite range of possibilities by setting the position of the slide at will. The difficulty was to emulate the different possible transitions when using the slide.

      One playing technique unique to the trombone is due precisely to the possibilities offered by means of the slide; the trombone can play a glissando like no other. This technique is very delicate and takes a lot of work to master with the real instrument, but luckily, the technique is put at the disposition of all BRASS users in a way easily accessible.

  • Saxophone:

 

      Saxophone model is very different from trumpet model. It is not the lips which are producing the initial vibration, but a reed. It is much more complicated to modelize the saxophone architecture, with all the holes and keys and their playing configurations.



 System which allows to measure the resonances of a real tenor saxophone. The measurement is done on the acoustic impedance of the instrument input (acoustic impedance = acoustic pressure / acoustic flow)

 To play the saxophone, the saxophonist pushes his bottom lips firmly against the reed and his top teeth against the mouthpiece/nozzle. The pressure must be equal in force: neither too strong nor too weak. The position of the lips on the reed is also important because if the nozzle is pushed too far into the mouth the pinch of the lips will not have enough control over the reed, but if it is not pushed in enough, the vibration on the length of the reed is reduced too much.

     

 

 

Once he has found the right amount of pressure, the saxophonist breathes in the instrument by increasing the pressure in his lungs and mouth. Once again this pressure must be strong enough to inject the proper amount of energy into the instrument allowing it to create and maintain the oscillations, but not so strong that it risks holding the reed against the mouthpiece, closing off the entry of air.

      It was the task of the researchers to re-create the process described above, include the physics of several other elements (the attack, timbre, and noise for example), and from that re-creation bring you the saxophone model you have in BRASS.



Division cadre

THE RESEARCHERS     


BRASS is the result of the work of the Arturia team and IRCAM, a Paris-based research facility. Without IRCAM we could not have brought you BRASS and therefore we offer them much thanks for all that they have contributed.

Ircam is dedicated to contemporary music research and creation. It remains a unique place in the world, where musicians and scientists work together to find new ways of producing sounds and music and to link art and science.








The project of wind instruments modelization took many years of research. Xavier Rodet, from the analysis-resynthesis department of IRCAM, and Christophe Vergez, currently researcher at CNRS/LMA were the main actors of this research. André Almeida worked on the saxophone modelization, and René Caussé on the mutes modelization. Xavier Rodet and Norbert Schnell worked on the chorus section, and Patrice Tisserand worked closely with Arturia and IRCAM team on the code implementation part.

Ircam physical models are based on a technology called Non-linear Multiple Feedback Loop. This technology brings far more realism than Waveguide models developped until now. Historicaly, the first model achieved was the trumpet model which could only be played from a breath-controller. Arturia and Ircam managed to adapt this model to a keyboard interface. The riff mode was developed by Arturia on the premises of the existing three models.

Unison instrument multiplication A special chorus technique has been developed by IRCAM to play several unison instruments with a high degree of realism. With this technique, you can even place your different instruments in the stereo field, like you can do with real players.