Tempo mark causes margin trouble [SOLVED]

For some reason, when I add a tempo mark at the start of this music, Dorico forces the bottom system to the next page. It may have something to do with the vocal Player holding three vocalists. I can use Frames to force the wandering system back (there being plenty of room for it), but I would rather not.

ItWasALoverFragment.dorico (663.0 KB)

I would have thought that if you reduce the inter-system gap slightly (in Layout options > Vertical Spacing) Dorico will fit the third system on the first page. It’s worth looking at the percentages shown in the bottom right corner of each page when the Engrave > Staff Spacing mode is used. I suspect that with the third system on that page, with no tempo marking, it’s close to 100%, and that the tempo marking would push it over 100% so Dorico automatically pushes the third system to the next page.

I’ll take a look at that. I have added a fragment of the Dorico file now to my original post.
This has happened on another file earlier that I used Frames to solve. It was another file in which the vocal Player held two singers, but another couple of files in which that was the case did not need frames to reign them in, although they filled out the first page by expanding distance between staves and systems. Even in those cases, using frame breaks restored the third system to the first page.

Thanks, Leo, for responding so fast.

It’s difficult to know exactly what Dorico’s threshold is for bumping a system onto the next page, but if you set that Inter-System Gap to even 9.9 spaces (down from 10!) Dorico keeps the third system on the first page.

Alternatively you could reduce the bottom Music Frame Margin (Layout Options > Page Setup). Again, reducing that from 10.58mm to 10.52mm (a very tiny amount) persuades Dorico to keep the third system on the first page.

There are various other things you could tweak by tiny amounts that would result in the same thing; the point is that your material is just on the cusp of being too tall for the current settings.

Thank you, Leo.
Next time I’ll think to try that myself.