What is the first step in arranging a jazz or pop song into piano? I find composing classical is a little easier, but I would like to try jazz and pop. I'm a little bit confused because I don't know where to start. One of the songs I would like to try is Hello by Adele.
There is a simple, direct answer to the question as stated initially: "What is the first step in arranging a jazz or pop song into piano?"
For me, that means listening to get to know the whole song (all instruments and vocal lines) and to identify what's essential. Since a piano arrangement is constrained by the technical limits of two hands, one must usually omit some of the original instrumentation.
You've picked an interesting example - Hello by Adele.
It's a good example of a common type of current pop song. A very simple basic musical structure. Just four chords, repeated over and over, with some slight variations. Apart from a pervasive four-note descending scale there's no real melody, the vocal style might be best described as 'emotional riffing over the chords'.
The song starts with bare piano chords (which I guess you'd have no problem transcribing?) Tension builds, drums and pads are added, but there's no additional musical content, nothing you could really add to a piano part, except 'play louder!' You COULD transcribe Adele's vocal filigree note-for-note, I'm not sure it would be particularly useful.
There are several piano/vocal versions of 'Hello' available online.
This one attempts to include the vocal line in the piano part.
This one offers, in my opinion, a more useful piano part.
But, anyway, there's two approaches to making a piano part for the song. Personally, I don't think this song requires or deserves any more than something like this, preceded by a couple of written-out bars to show the rhythm.
And be careful. That basic piano pattern that you hear in he first part of the song underpins the whole song. If you lose it in an attempt to add more intensity, the song collapses.