Notation For Repeats

[David Barnert]

Another thing to keep in mind, by the way, is that the abc standards have changed over time and the process continues. Most of the early software (for instance, BarFly, which was actually later than some of the others, but no longer runs on modern macs) are based on abc version 1.6, which was the standard for many years. But newer software (for instance, EasyABC) are based on abc version 2.1, which has some significant differences from 1.6, worked out about a decade ago. 2.2 is already in draft form, so things are constantly changing.

[Steve Mansfield]

Very true, but the repeats notation hasn't altered for many years.

 

Whilst in abc geek mode it's also worth mentioning that abc is also fully backwards compatible, in that anything introduced in later versions of the spec won't break anything legal in earlier versions ( with the notable exception of the old Abc2Win line break character which was specific to that programme and never part of the official spec).

[Jack Campin]

However, if you use some spiffy recently introduced feature there is a good chance that a lot of people will have software that can't process it, and they'll be left looking at a piece of uncommented alphabet soup with no way to guess what you intended it to do.

 

This is more of a problem now than ever before, with mobile platforms of various kinds all introducing different limitations.

 

Unless you have a very good reason to the contrary, try to keep it simple in anything you make public. And if you do use tricky features, explain them (preferably by supplying audio and score files generated from the ABC source with your favoured software using the versions current at the time you're writing, or by uploading the source you transcribed from).

[Don Taylor]

A problem is that while there is at least a semi-formal definition of ABC code, there is not a definition (AFAIK - anybody?) of the underlying music notation - instead there is a general understanding of what things mean, but there are ambiguities and repeat signs are one of the ambiguities.

Jack has hundreds of tunes in ABC notation on his web-site. Many of them have an AABB phrase structure, here is an example of how he notates these tunes in ABC:

 

X:6
T:The Battle of the Somme
Z:Jack Campin, 2006, http://www.campin.me.uk/
M:9/8
L:1/8
Q:3/8=90
K:D
A|f<af d3 d>cd|e>dG B3 A3|B>GB A3 d3|f<af e3- e2
A|f<af d3 d>cd|e>dG B3 A3|B>GB A3 f3|e>fe d3- d2:|
A|d>cd e3 A2e |e>fg a3 d3|d>ef g3 A3|f<af e3- e2
A|f<af d3 d>cd|e>dG B3 A3|B>GB A3 f3|e>fe d3- d2:|

The first repeat takes us back to the first bar, fine, that way we get the AA, but what should the second repeat do?

The 2.1 standard says:

"Recommendation for developers: If an 'end of repeated section' is found without a previous 'start of repeated section', playback programs should restart the music from the beginning of the tune, or from the latest double bar line or end of repeated section."

If you plug Jack's ABC into, say, EasyABC then you get exactly this, which gives us the BB phrases. So Jack is correct in his notation for ABC.

 

But if you enter the same notation into Musescore, which is not an ABC player, and play the result then you get AABAB, the second repeat goes back to the beginning of the piece, not to the end of the last repeated section.

Which interpretation is correct? And, perhaps more importantly, how do you know which is correct?

Personally, I prefer to use explicit 'start of repeated section' markers like this:

 

|:A|f<af d3 d>cd|e>dG B3 A3|B>GB A3 d3|f<af e3- e2
A|f<af d3 d>cd|e>dG B3 A3|B>GB A3 f3|e>fe d3- d2::
A|d>cd e3 A2e |e>fg a3 d3|d>ef g3 A3|f<af e3- e2
A|f<af d3 d>cd|e>dG B3 A3|B>GB A3 f3|e>fe d3- d2:|

 

This gives AABB in EasyABC and when notated the same way in Musescore it also gives AABB.

 

You could argue that both ABC and Musescore are notation systems and the fact that they attempt to play the score is a bonus that should not be taken too seriously.

 

Don.

 

 

Edited September 13, 2016 by Don Taylor

[Roger Hare]

...If you plug Jack's ABC into, say, EasyABC then you get exactly this, which gives us the BB phrases. So Jack is correct in his notation for ABC.

 

But if you enter the same notation into Musescore, which is not an ABC player, and play the result then you get AABAB, the second repeat goes

back to the beginning of the piece, not to the end of the last repeated section...

 

...Personally, I prefer to use explicit 'start of repeated section' markers like this:...

 

It was precisely such a situation which prompted me to try getting around it with the use of P:, and also to post

my original query. I too now use an explicit 'start of repeated section' marker as default.

 

R

[Jack Campin]

Well I tried to follow that up.

 

See the thread I started about "Posting when not logged in".

 

I might try to reconstruct what I wrote someday.

[David Barnert]

It was precisely such a situation which prompted me to try getting around it with the use of P:, and also to post

my original query. I too now use an explicit 'start of repeated section' marker as default.

 

As I see it, the basic ambiguity in the relationship between repeats and P: fields is this...

 

X:1

T:Whatever

M:C

P:A2B2

K:C

P:A

|:da da da:|

P:B

|:de de de:|

 

This code, literally interpreted by an abc app will come out as AAAABBBB, rather than AABB, which was probably intended, because the repeats and P: fields are redundant. In other words, a standard 32-bar fiddle tune of the form AABB should either be notated with repeats or P:, but not both.

 

And if it's not so well-behaved a tune, with numbers of repeats that cannot be unambiguously expressed in classical repeat notation, and you use P: to get around it, does that invalidate any written repeats or add to them?