Editor uses four spaces per bar for Waltz-time

[pdxdjazz]

Here is some previous discussion.

http://www.irealb.com/forums/showthr...or-waltz-style

http://www.irealb.com/forums/showthr...0409#post20409

You can certainly lay-out a chart with 3-space measures, but it's not necessary.
)BOB