If, in Kontakt, you assign two voices to "Violin I KS Combo" and then play a scale starting from G2, some keys will play a short tone, others a sustained one. G2 to A#2 are short, B2 to C#3 are sustained, D3 to G#3 are short. A3 and A#3 are long notes, and all the notes from B3 on are short.
How many voices does each note use in GPO? I guess two; but "Timpani KS", for example, are given 64 voices of polyphony by default...
First of all, I'm assuming that you are referring to the section instrument "1st Vlns KS Combo." When you load it into Kontakt (or the player, for that matter) this patch should default to a polyphony setting of "32." It’s best to leave this instrument set to that value. Being a keyswitched instrument the polyphony requirements at a given moment depend on many things: Which KS you've selected, how many notes you are playing, and the type of note overlaps you are creating (are among them.) For instance, the first keyswitch is a Sustain+Short which is a layered instrument. It layers sustains and short bow samples. A single note played will require 4 notes of polyphony. A 4 note chord will require 16 notes of polyphony. If that chord is sustained and then followed immediately by a second 4 note chord the possible note overlaps could briefly increase the polyphony demand to 32 notes. The pizzicato KS, on the other hand, requires only 2 notes of polyphony for single notes so similar conditions will demand half as many notes of polyphony. The instrument is set by default to "32" so that most common situations are covered. It doesn't hurt to have a higher number than you actually need. If your part only demands 8 notes of polyphony, setting the polyphony to 32 doesn't consume any more resources than setting it to 8. Having a higher number gives you "room" to work without concern. The only time restricting the polyphony is wise is when an instrument is regularly consuming massive amounts of polyphony because of a long naturally occurring decay. Instruments like piano, harp, and timpani fall into this category. It's often wise to limit these instruments to 32 voices or less to get lower CPU usage.
On the subject of keyswitches, be sure to read the .pdf documentation posted in the General Discussions section. It explains the location of and identification of all of the keyswitches.
Check out the thread from last week on the Timpani KS instrument. The polyphony setting of "64" for this instrument is incorrect. I even posted a modified file to replace this instrument with a more efficient version.
One other thing: As noted in another thread in the last few days, when you load the updated library into Kontakt you must take steps to add cc21 data to the beginning of your tracks. The value of cc21 should be about "64." This is necessary because the new version of the library has a "length" feature now and instruments load with a default setting into the player. The full version of Kontakt doesn't have this ability so you must supply the default value manually. Otherwise, instruments load into Kontakt with too long decay/release times - double what they should be.
I just realized that I didn't make it clear that if you use the proper (higher) polyphony settings you will not hear the things you described. The "short note, long notes, short notes, etc." effect is due to the priority given to different layers of samples that only becomes audible when you starve the patch for polyphony with too low a setting.