Showing LilyPond to a friend is sometimes tricky. The question: "Oh, can it do this or that?" easily pops up.
I "survived" the BendAfter question, but had to let go for a BendBefore (or 'doit'?) example.
Diving in at home later that day I found some interesting things done with a new(?) BendSpanner-grob for a guitar, and several people having put a bounty for further work on this. This goes back to 2013, 2016, 2019, apparantly not an easy question. The BendSpanner-grob example goes way behind what I probably ever will need, in fact I would probably have enough with the coding for (some of) my examples.
I've extracted 3 examples in 3 .PNG-files, attached. If you want I can also put a bounty out for this ($25 for each example via PayPal?, first come, first serve). My bending is aimed at a bass clarinet, but that is probably irrelevant for you.....
The 3 examples:
1:
(the bar-number "12" is irrelevant, btw.)
2:
3:
Can someone help me?
Regards,
Wim.