The master rolls for player pianos were made by actual pro players playing in real time. They needed to have the performance chops, even if they maybe were not

The master rolls for player pianos were made by actual pro players playing in real time. They needed to have the performance chops, even if they maybe were not the composer in every case. This quote about "separation of composition from performance" applies when you are working with a sequencer because the composer can "step-edit" the musical data note-by-note into the sequencer and then have the sequencer play it back in proper musical (real) time.