Metrostyle (no hyphen, and capitalised as shown -- it was a trade name)
rolls are virtually all metrically arranged.  They are made from exactly
the same master rolls used for rolls issued without the interpretation
line (e.g., on Aeolian's "Universal" label).  The only thing that makes
it into a Metrostyle roll is the addition of the Metrostyle line!
Metrically arranged rolls rarely include any tempo effects cut into the
notes directly, although some pauses are edited in on better-considered
rolls.

The red wiggly line was simply a musical editor's suggestion about how
the piece could be played, and Aeolian expected that once you'd learned
the piece you would feel free to interpret it as it suited you to do
so.  Most such lines were produced in the factory -- in the UK by
Reginald Reynolds, amongst others.

There was a series of "Autograph Metrostyle" rolls where a famous
artist's performance was indicated by the line.  These were produced
by editors who refined them until the artist approved; I'm sure the
direct operation of levers by the signatory was rarely done (the idea
is clearly absurd).  See my post in MMD 20011004 for the roll editor's
own description of how the Greig Autograph-Metrostyle rolls were
produced.  This shows just how seriously Aeolian took the whole
venture.  Sousa's rolls would have been done similarly, I'm sure.

The entire point about the Pianola was (and is) that it was a musical
instrument, letting you input exactly as much musical creativity as
a pianist would into playing the piece by hand.  The Metrostyle set you
off on a good path and acted as a reminder.  You could always pencil
your own interpretation onto the roll if you wanted to, and marked-up
rolls turn up fairly regularly.

Metrostyle rolls were manufactured in the factory by copying a master
using a pantograph system, and the quality obviously varies according
to the attention being paid by the operator.  They are frequently
derided, but actually if you can be bothered to be a little intelligent
in using them you'll often find that the lines make a fair degree of
sense.  I recently got a roll I'd been searching for and played it
alongside my favourite CD performance.  To my great surprise, the
Metrostyle line was exactly (and I mean exactly) the same!  Oddly
enough, I've not tried any other rolls to see how close they come.

My answer to Paul Murphy's question about how much interpretation
to give Metrostyle rolls versus other rolls is "exactly the same":
you give as much (or as little) interpretation as you feel makes the
right performance.  The printing on the roll shouldn't come into it!
If you can tell it's a Pianola and not a hand-played performance then
you're not using the instrument properly...  so goes the theory.

Rather to Aeolian's chagrin, a lot of people liked the instrument when
it sounded like a Pianola, and that side of the hobby has almost totally
deadened expectations of anything higher, which is a great shame.

Julian Dyer