I define abstract music as that which has an absence of Song, Dance or Narrative.
I locked onto the term "Style Sheet" as something that states in an idiosyncratic way my concerns in advance of composing a project, or a way to begin a project.
First of all we need to begin with the central concern of the music. That is, whether that is harmonic, rhythmic, or conceptual, for example.
Secondly, what variations there are of this. A cross-rhythm, a harmonic variation, a melodic variation, for example, used in the composition process.
After that, there are music-specific concerns; scale/key concerns for example.
In my Style Sheet, I state my interest in Octonic Scales. Not the one defined just as the Octotonic Scale (i.e. the two consisting of alternating tones and semitones). Octonic Scales are any made up of four of each, tones and semitones, in any order.
Next, for me, rhythm. I don't think of rhythm as something that risks the "dance", taking my music away from abstraction I desire to achieve.
I have the concept of a "core rhythm" which is rarely stated in its entirety but at which any pitch/event may be represented.