What's a sub-bracket?
It's not often that I feel like I've explored every aspect of a problem and come up empty, but in this circumstance, the feeling is warranted. The subject is instrument sub-brackets. To bring us all up to speed on this tiny bit of arcana, please examine the examples (click for a larger version) and away we go!
In full scores, instruments are bracketed according to group, then subgroup, then (very rarely) sub-sub-groups. In the example before us, we see the flute section from the Rite of Spring. The big bracket is for woodwinds, the first sub-bracket for flutes, and the sub-sub-bracket for Flutes 1 and 2,3. In older scores, sub-brackets were frequently drawn as braces (the curly bits to the left of piano staves) rather than brackets. Neither Finale nor Sibelius handles these situations very well, but MakeMusic's software does a better job than Avid's.
The crux of the matter for me is the gap between brackets and staves. Please notice on the original that the sub-brackets do not go through to the staves. The hook on the sub-bracket stops when it intersects the larger group bracket. The sub-sub-bracket's hook stops when it intersects the sub-bracket. This particular style is possible only with great effort in current engraving software.
Is there a generally recommended style?
In my entire collection of standard engraving reference books, the issue is barely, if at all addressed. Ted Ross mentions only one sub-bracket, Gardner Read indicates a preference for braces instead of brackets, and the usually reliable Stone doesn't even mention brackets at all in connection with scores. In many published scores that I have examined, this seems to be a choice colored by region, date and publisher. So it is not surprising, perhaps, that neither Finale nor Sibelius offers the option to specify the length of the sub-bracket's hooks. (I am not familiar enough with Score to render an opinion, but my understanding indicates that such a specification is possible.)
That said, Finale is the only package capable of delivering usable sub-sub-bracketing. Finale's system of grouping offers much finer control than Sibelius does. I can define an arbitrary number of staves to be part of a staff group and assign any of six bracket options. I can individually adjust the line thickness, distance from the left hand of the staff and adjust the top and bottom of the bracket. With these tools, I can create sub-sub-brackets that behave correctly under any given circumstance, even though the hooks run through to the staves.
I'm sorry if this is getting too nitpicky, but one of the reasons that Finale is often touted above Sibelius is the near-infinite adjustability of items. I'll continue at risk of losing some of you.
Mind the gap?
Finale's sub-brackets have a hook length of about 1.5 spaces. This means that I can achieve the desired gap by simply moving the sub-bracket over so that the hooks are buried inside the big bracket. The problem, as should already be apparent, is that the sub-bracket now sticks out too far. To extend the technique to the sub-sub bracket results in an uncomfortably oversized mass at the left edge of the staff. The only option, therefore, is to have brackets that protrude through one another – a valid choice, but one that I would prefer to have left up to me.
Sibelius doesn't offer much control at all over bracketing. I can only feasibly create one level of sub-bracket. The only adjustments available to me are the distance from the left of the staff, the number of staves enclosed, and line thickness. Even so, it might still be possible to implement a solution similar to Finale's, except for one thing: the distance from the left of the staff is a global variable. All sub-brackets are equally affected, affording me no way to differentiate a sub-sub-bracket. Further, no matter how far left the sub-bracket is positioned, the hooks always connect to the staff. This makes it impossible to maintain the gap even on the single sub-bracket allotted me. The only way I was able to accomplish the above example is by creating a one-off line and manually positioning it.
In fact, the only way to achieve the desired effect in either program is through painstaking and fussy effort. In Finale, I would be required to define a specific bracket shape expression and attach it to the appropriate position on every page. Such shapes would not update to changes in either staff distance or measure reflow.
My conclusion? Live with the brackets going all the way through to the staves. It's not worth the substantial effort needed to effect such a minor detail. I do prefer the cleaner look afforded by the gap, but not enough to go through the hassle.