Oops, I misunderstood the title of this thread. I thought you were referring to the four-string kind: I have two...

… lucky you. Works perhaps better than the clicky one I use :-(

I just opened a keylayout file that I created some years ago with Ukelele. It prompted me to add some missing keys and I said yes and opened it. Looked fine. I saved the new file and re-opened it with Ukelele 2.1.4. Looked fine as far as I can tell. What was the mess you encountered?

Well, I opened a system keyboard and began to customize it. Then I closed it, changed something with the font to be used and wanted to re-open the ukelele-file. “Error message”, not to open.
There are some PUA codes in it. Could this be the problem? I hardly believe.

I'm not sure but I think it's because you modified an existing system keyboard. Did you give it a new name and new identifier number? That's what I usually do. If I'm not mistaken, that was a MUST in Ukelele guide. I have used PUA in the past without any problem.

There's a Google group for Ukulele users: http://groups.google.com/group/ukelele-users.

Thanks for your suggestions! However, while it seemed to have worked this afternoon (yes: new name, new number, saved as …) this evening it fails again to re-open. Three hours work – trashed?
Instead of opening the file (not even with manually adding "…keylayout" to the file name) I get this kind information:

Unfortunately I lack humor for that sort of notification …
What the devil is going on?

Or, to ask otherwise: is there an alternative to Ukelele?!

Actually the message seems really helpful. .keylayout files are XML, so you could check with the help of a text editor what’s going on in line 549.

– I did! See this part of the file:

I tried this: I changed the little black squares into an ordinary ASCII char. and saved the file. Whooops – Ukelele does open it! But I wonder: there are many other F8xx or 1Dxxx characters which now seem to cause no problem. At the moment (no further alterations made) the file closed re-opens normally.

Still don’t quite understand that syntax of the xml file completely.

Does the very recent update of Ukelele 2.1.5 have something to do with your problem? The update message says it gets around an apparent bug in Apple’s XML parser at some characters outside the Basic Multilingual Plane…

Sorry for being late on this. Yes, the release of vs. 2.1.5 has been induced by John Brownie dealing with the problem I’ve reported to him. He has been very responsive on a fast pace and, as far as my own workflow concerns, it does work for now.

And this is now how I got my physical keys to properly display what I want them to show:
.

I have not yet come across a better solution for that, though.

http://www.artlebedev.com/everything/optimus/
Has it ever shipped?

Andreas, I see you're dealing with white mensural notation, i.e. my field of interest. Is what you're working on is something that could be checked out or read about?

Not even close, but I still think this is a fantastic piece:

http://www.youtube.com/watch?v=puSkP3uym5k

Christopher, I never thought I'd be head-banging to the sound of a ukelele!

Riccardo: I don’t believe it has ever shipped. I’ve not heard of it.
(But I wonder why Apple doesn’t embark on this.)

Grzegorz: I deal with the composing of a comprehensive book on early musical notation. The first volume is expected for autumn this year. This is the author.

Christopher: this IS fantastic. I will train to handle my keyboard as he does with the cords ;-)