It looks like the glue released at the joint (got hot/wet maybe?). If that's true, the glue could be hide glue and repairing with hide glue should work.
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My viewpoint, and I dabble a bit in each, not particularly good in any.
Visual; SMN for general or universal use, TAB for specific instrument, archives a specific variation of a tune/song.
Audio; storage devices [cd's, etc], individuals, archives a specific variation of a tune/song.
Both work, but not necessarily for everyone.
Each should be used as the situation indicates.
Stumalia hit the nail on the head in her blog.
What I called HD tab is really just the note names below the SMN just like MD tab. It makes it much easier for me. Tabledit has afeaturethat allows you to change between the tab numbers and the note name with just the press of a key [actually 2 keys, shift and 4, the $]. I also use the reverse tab function so any 'stacked' notes, like chords, read the same vertically as the SMN, bass notes at the bottom.
I used Musedit for a long time for MD tab. It's a good program and he did make it free but the programmer isn't working on it any more. I switched to Tabledit and found it good for the MD and it has a couple of features that lend itself to setting up MD tab for the HD if you don't read SMN very well. The programmer is very responsive to his customers also and he has a web page for customers to post comments etc. You may want to check them both out to see which youprefer. I feel they are both about the same as far as learning curve.