I am playing around with parts with no barlines, like in part books from the renaissance.
Have a look at this –
This rest sums up to 7.5 semibreve (whole note) rests, but I never saw any such notation before. What do the dots mean in this context? How shall one read it?
If you look at most 16th/17th-century partbooks, you’ll see they used “long” rests (as shown in your example), then breve rests (1 whole space), then semibreves and minims roughly as we have them now (though taller and thinner).
Long rests would be paired and stepped on different staff positions:
What’s interesting is that you’ll often find patterns like this:
… so that even though the tactus is on the semibreve, there’s still a notion of where the breves fall.
Dorico caters for “Old Style” Multi-measure rests (which you’ll find in instrumental parts up to early/mid 20th century), which are clearly based on the Renaissance rests: