Bible-regals are very small regals, whose front block, i.e . keyboards, pipes and wind-chest can be hidden underneath the bellows, which are hinged to each other. Since these bellows often are made as book-imitation, it is called bible-regal.
Unfortunately I could never make an instrument of this kind, possibly because one would not expect them to work reliably and musically convincing due to their enormous compactness. Even Michael Praetorius doubts that in Sytagma musicum.
I reformed two existing copies of historic bible-regals. The results were very satisfactory. I had one recorded in two representative videos with Jan Katzschke. The recordings prove that rich sound colour as much as remarkable fundamentals serve both for accompaniment and for agile solistic playing.
On another video I filmed myself when making one stop of regal pipes in late 16th century style for a colleague.
True enthusiasts may enjoy a small recording of the chapter in Syntagma musicum concerning the regal.