I agree Grishka - when you do post a tune, you'd like it to appear the same to everyone!

To summarize the current state of play, abc 2.1 is the current standard and this is what people should try and adhere to at the moment. But note that the intention of 2.1 was to iron out problems relating to single line tunes; various things relating to multi-voice tunes are liable to change.

To get an idea of the proposed changes to 2.1 being envisioned have a look at abc 2.1 proposals, which contains links to the main areas of proposed change from 2.1 to 2.2 (or 2.2.1 for minor changes). These relate mainly to how to handle multivoice tunes in a manner which will make them unambiguous (various points of synchronization and control between the various voices).

There is also a lot of discussion about the stylesheet directives (or alternative equivalent specification), particularly the things relating to printing tunebooks, giving greater formatting control down to page level, with commands having scope at file, tune, movement, and page,levels. This appears to have generated a lot of discussion and I if I read Chris Walshaw's comments correctly is likely to be left for a later revision of the standard.

One of the problems is the stated desire or Chris Walshaw's to maintain backward compatibility with the old versions of abc out there (of which there are no doubt countless files). This is a problem for software developers, since they have to allow for various old constructs as well as supporting the new ones. Personally I would favour being stricter about a new standard, but provide converters to bring old files up to the new standard. For really old files (abc 1.6 and 1.7, there would be very little change to make - only add an abc version header in many cases). From various version of the 2.0 standard there might be more to do, but while 2.1 is relatively close to 2.0, now would be a good time to make the converter. I would aim to make 2.1, or maybe 2.2, an enforced standard for new/updated software.

Mick