Hey, yeah I can talk about how I go about doing my demos.
I have too ways of doing them.
One is I pick an instrument or two from Pianobook that I like the sound of and I write from scratch using them instruments and some of my own collection that I own.
The second way is I pick an existing track of mine and change one or some of the instruments I used with Pianobook ones.
I tend to write pretty melodically so a lot of my music has a theme.
Also I decided mainly to use full pieces with loads of instruments as it helps people hear what that instruments sounds like blended in a full piece with other instruments.
Also it is a great way of getting your music heard.
Hopefully I pick or write tracks that people will find enjoyable.
I do write very quickly but I must say I am a lot better at writing music than I am of mixing it but hopefully people get the gist of what I wrote. 🙂