Thanks for the replies.
To clarify - I understand the concept of MIDI and the idea of rendering using samples - did sequencing in Ableton.
I was not sure if Real instruments qualify as such but it seem that they mostly exist as phrases not single notes.

My particular purpose was learning melody of a jazz standard - using melody that comes with MGU file.
So it was just a question of rendering it in somewhat pleasant form - not really using it as part of my recording.
As the next step I would mute melody, render backup track, import it (whole or separate parts) into Reaper and record
melody and solo parts myself.