Barline connection across staves — which groups share a continuous barline

Staves get a CONTINUOUS barline through the whole group when they belong to one keyboard/harp instrument, one choir (short or open score), or one orchestral family bracketed together. Barlines do NOT connect across genuinely independent solo staves in a concerto (soloist vs. orchestra), across a written-out cadenza (barlines suspend for the soloist while the orchestra's rest is barred normally), or between unrelated instrument families sharing a page.

A keyboard/SATB/open-score fugue block whose staves render with independent (non-continuous) barlines per stave.

Gould (Behind Bars, systems chapter — barline grouping by ensemble type); Ross (The Art of Music Engraving, practical grouping guidance for mixed ensembles: 'group what functions together, not what merely sits adjacent').

This rule is about where marks land on the page, so it can only be judged after engraving. Collision and spacing faults live here.