creating a function to automate slides in guitar music

[John Doe]

Hi, LilyPond users,

First post, here. I'm trying to create a function that adds falling
gliss lines to a note or chord, as commonly seen in modern guitar
transcriptions. (N.B. I'm talking notation, not tablature.) I posted a
a question on [StackOverflow][so] which led to a rough working
version, but it only works reliably if music is entered in absolute
mode. Naturally, I want it to work everywhere! So, I broke down and
subscribed to this list.

I want to model a function on the [example][ex] in the snippets documentation:

    \afterGrace d'\glissando { \once \hideNotes g16 }

If I could access the pitches of the music given to the function, I
could possibly just write a grace chord down a few steps and avoid the
issue of whether it is absolute or relative. How can I access the
pitches of the given music (note/chord) to accomplish this?

I probably haven't thought this through all the way either, so if
anyone knows how to solve this problem (or if it's already solved),
input would be greatly appreciated.

Thanks!

Randy

[so]: 
https://stackoverflow.com/questions/54477548/lilypond-giving-no-space-to-an-invisible-grace-note-in-a-music-function/54477549#54477549
[ex]: 
http://lilypond.org/doc/v2.19/Documentation/snippets/fretted-strings#fretted-strings-slides-in-tablature