Tutorials: Suggestions on advanced/incipits tutorial

[mfeustle]

The current tutorial is a very effective summation of just about everything covered in the basic tutorials. For discoverability, I wonder if the title could also reflect that to those looking for practice solidifying what they have learned.

One small issue on the "first note" step is the presentation of the example with the closing </ tag. For consistency, it may be worth using the "usual" empty element tag.

I would suggest a few clarifications on the final step of the tutorial, which introduces slurs and the use of xml:id: When I first attempted the tutorial, I initially read the "1" in the "d1e" identifier as a lower-case "L." I imagine others have gotten tripped up there.

More guidance could also be present on the callouts of the xml:id identifiers in the final rendering of the slur [slur staff="1" curvedir="above" startid="#d1e4614" endid="#d1e4615"/]. It is not clear from the current accompanying text how or where to use the "#" symbol, and depends on the user's perseverance in trial and error perhaps more than we would like.