I am binding to ListBoxSelect and i want to implement a function which recognizes an alphabetical key-press and uses this to jump to the corresponding place in an alphabetically sorted list.
Is there a way to tell what type of event is flagged by ListBoxSelect? I see something in the documentation about getting event "keysym" but i dont know how to access this.
No, there isn't a way to tell what type of event is flagged by <<ListboxSelect>>. Using <<ListboxSelect>> is useless for binding to a letter key, however. It only will fire for mouse clicks and using the arrow keys to navigate the listbox. 
You can bind to <KeyPress>. That binding will tell you what key was pressed, and in that binding you can change the widget's selection. You can get that information from event.keysym
How to determine the type of event flagged by <> in Tkinter?