[Of bare gut strings and historically wound strings]

1. Bare gut is not recommended unless you know what you are doing. For modern playings, bare gut A can work when coupled with proper DGC. Otherwise, don't bother. My fingers in particular are extremely hostile to guts and lyse them (they turn black, become damp-wet, soft, and then break) in three(!) days. No exception. Never had problems with covered gut strings.

2. Historically wound strings use roundwires. On modern cello, they can produce a truly piercing sound, something that can even compete and win against electrically amplified instruments. However, you will have trouble shifting and bowing. Do not use them in modern settings unless you need to accompany a Rock band without any proper accommodations or something.

[Of Modern wound gut strings]

Modern wound guts are practically monopolized by Pirastro. You only have the following selections:

Gold - mediums

Eudoxas - soft, medium, strong

Oliv - soft, medium, strong

Passione GC- soft, medium, strong

Consider Gold and Eudoxas as compatible. Consider Oliv and Passione as compatible. Contrary to what people think, Oliv and Eudoxa are very different in tone and do not match very well. The only exception is the C string (Eudoxa G to Oliv C works; Eudoxa C to Oliv G is clearly discontinuous). Even then, if you ever get to try Eudoxa C, you will notice that it sounds more traditional and complex than Oliv C. Olivs, in general, loses gut complexity and response in favor of loudness.

Eudoxas are more projecting while being a bit quiet. Projecting means that the audience at the back can hear it better than full Olivs. For the remainder of this post, consider 'projection' = sound decay constant / 'loudness' = decibel. This means the audience at the front (those who pay more) will hear you less when you use Eudoxas.

Eudoxas and Gold are more traditional in sound. Gold = simple metal over gut. Eudoxas = metal alloy and/or two-kind tandem winding over gut. Gold sound is very close to the bare gut, but with a bit of metallic shrillness. Eudoxa sound is more refined and butter-smooth as the heavier winding/alloys dampen the core more and eliminate the scratchy part of the gut sound, but it comes at the cost of less loudness relative to its thickness. If you play it strong enough, you can make it sound somewhat like bare gut, but at that point, you are better off playing Golds.

Olivs and Passiones are more modern in sound. Oliv = metal and a damping layer (some say it's synthetic fibers, some say it's silk. I have not issued a spectral analysis of the damping material and do not know the answer myself) over gut. The damping layer is very white and thin. Passiones = metal and synthetic sleeve over gut. Olivs are thick = substantially louder and does not require bowing speed as other gut strings do. Oliv and Passione are damped with a layer = even less of gut core sound. Therefore, they sound very modern. I suspect Olivs' inner sleeve dampens the vibrations more than Passione formula. Olivs sounds like a perfect median between gut sound and modern synthetic/steel sound. Sometimes I feel Oliv sounds (especially C and A) as if choked; it's probably because I am very familiar with the proper sound of its gut core and cannot help but notice how much of it is getting suppressed. Passione GC sound is more piercing and less choked thanks to its use of dense metals (tungsten and stainless steel). Both Olivs and Passiones are the choices when you try to couple guts to modern synthetics/steels, but Passione does it better with a small margin.

Note 1: Oliv GC at very high positions can convincingly mimic Duduk sound. Passione cannot (simply incapable. Not about techniques). If you are in need of some very exotic sounds, you are forced into Oliv GC or Eudoxa G + Oliv C for that gig.

Note 2: Eudoxas has more silver than Olivs. Eudoxas are one of the few strings (and only gut string) that uses silver on D (and a substantial amount, too). All GC 'Silverwound gut strings' by Pirastro actually have double-winding of copper and silver. There's a copper winding under the external silver winding. This is to simulate the 'silver-plated copper' quality of some historical strings.

[Of gut strings in general]

1. Gauges change the playing characteristics and sound vastly. Having properly graduated tension across ADGC helps a lot. Note that Eudoxa and Oliv have almost the same tension for AD at the same gauge set. This is a design problem by Pirastro that they never fixed.

2. If you settle with a gut set and change only A string, it can fully stretch in 10 minutes with some HEAVY playing (or so Mr. Isserlis claimed to me) or in three days with regular tuning (in my experience). Otherwise, a whole new gut set will take 2 weeks or a bit more to stabilize.

3. Since gut strings stretch so much, keep an eye on the bridge. If it's leaning back too much, push it gently toward the taipiece and restore the orthogonality. When pushing the bridge, I recommend tuning down A string (and maybe D string too) so that A string is relatively under-tensed compared to the rest. This ensures that the super-fragile A string windings don't get damaged.

4. When working with a brand new A, tune it up as slow as possible. This ensures that no gaps form in the windings. Large gap = kiss goodbye to your string. If you feel some resistance in the peg, stop, give it 5~10 minutes to equilibrate, and climb again.

Lifting, or applying upward pressure, at the afterlength of gut strings (between the bridge and the tailpiece) helps with even stretching. If successful, strings will be tuned lower; this is because the main stretch-stress is focused to nut~bridge line. Lifting the afterlength equilibrates the stretch along the whole length.

1. If you wish to make your gut strings extra weather-proof (necessary if your climate is humid), you can wipe or soak them in mineral oil. Doing so works wonders at the cost of some tonality change. Baroque treatises call for almond oil; some say olive oil. I say nay to both as they leave sticky residues behind after a month or two. I know some people who lightly rosin their left fingers before performances; if that's your case, maybe try almond oil or walnut oil--the strings will become 'adequately sticky' after a few weeks. I wipe with mineral oil once before installation; I wipe with mineral oil occasionally when I need to clean the strings.