Maybe the concepts of design are keys to create a music based on synthetic sounds.

Thinking with lines, shapes, numbers and colors helps navigate the never ending possibilities of a software like Pure data.

Harmony, melody and rythme can be insufficient when anything can be organised with such wide liberty.

Modes can appear everywhere, relations between harmonics and shapes can come out of places that used to be desertic.

Materials and dimensions, utility and necessity, drag creation in other directions.

A couple which I have just come across and am looking forward too.

Berio's Sequenzas Essays on Performance, Composition and Analysis
Dhrupad: Tradition and Performance in Indian Music

Sadly the Berio does not include Sequenza 12 for Bassoon, what can you do.

Oh great collection of books.

 This one is accompanied by a "Student's guide" from the same duo.  Exist multiple editions.