Classical Bass Line

I was playing the moonlight sonata and trying to improvise variations because i only know the start of the song, however, the bass line is actually really cool. You should try it out.

C#, B, A, F#

They sound great when played at a full octave apart

So jump up a octave with each chord?

This must be a minor progression because those C# and F# are the bookends setting the melancholy tone.
I've been enjoying the A(minor) & D(minor) chords.