*Note* for dynamic cross faded brass to work, your sfz player must permit the mod wheel to control 2 parameters at the same time, specifically cross fade point and gain. It is known that Sforzando from Plogue works. LinuxSampler does not.
What is Dynamic Cross Faded Brass?
Dynamic cross faded brass is the blending of low and high velocity brass samples based on the position of the mod wheel with the purpose of achieving a more realistic sound for long held notes. This effect is present in the -DXF labelled samples (trumpet, french horn, trombone) in the Standard Orchestra edition, and the brass (trumpet, french horn, trombone) in the Performance Orchestra edition.
Why do I want this?
Without dynamic cross fade, the tone of the instrument is fixed by the velocity of each note. Once the note is struck, the tone can’t change even if the volume does, but the tone of real instruments does change as the volume changes. A quiet French Horn note, besides a difference in volume, has a very different tone (or timbre) than a loud note. For short notes, this is fine. The problem comes when you want a held note with a crescendo (volume increase) or decrescendo (volume decrease).
What this means it that a choice has to be made when holding a note through a crescendo or decrescendo. What tone will be used throughout? Do you use the loud sample for both the quiet and loud parts of the note or do you use the quiet sample for both the quiet and loud parts of the note? Neither will sound realistic.
With dynamic cross fade, you don’t have this problem because both the low and high samples are mixed depending on the volume as controlled by the mod wheel. Play a note with the mod wheel set low and you get a quiet note with the low velocity sample. As the mod wheel is moved up, the volume increases and the amount of low velocity sample being used in the sound decreases as the amount of the high velocity sample used in the sound increases. This is more like how a real brass instrument sounds.
Here are 2 samples. The first uses the standard patches where the tone (sample being played) is solely determined by the velocity of the key hit. (In each case I have French Horn playing a minor chord, Trumpet doubles the 5th, Trombone doubles the root)
Without dynamic cross fade
Note in the above example, that the tone never changes. It is always the loud sample being used even when the brass is quiet.
The following example uses dynamic cross fading and the mod wheel determines the volume and the percentage of each sample that is heard. Notice how the loud brassy sound changes with the volume.
With dynamic cross fade
The above example is closer to how real brass instruments sound when the volume of a held note changes.
Controlling the crossfade instruments
Only Trumpet, French Horn and Trombone have dynamic cross faded versions. To make dynamic cross fade work, I need high and low velocity samples. I have only a single sample for each Tuba note so dynamic cross fade of the Tuba is not currently supported.
All the DXF (Dynamic Cross Fade) instruments (in the Standard Orchestra Edition) have “-DXF” in their file name and use the mod wheel (CC1) to control both the blending of the high and low velocity samples and expression (volume). The Performance Orchestra edition also uses dynamic cross fade but does not need the -DXF label because all samples are controlled the same way. CC7 is also available for separate volume control but has no effect on the blending of high and low velocity samples. Although most of the volume control is achieved though the mod wheel, the key velocity still has a small effect. A very light touch and a hard strike will sound different but not as much as if a non DXF instrument were being used. This is useful for adding more variety to staccato notes (or any articulation) above and beyond the mod wheel setting.
The dynamically cross faded versions of the “normal-mod-wheel” articulations, no longer use the mod wheel to control the attack time of the sample because the mod wheel is used for dynamic cross fade so the attack time is instead controlled by CC73 (attack time)