So when I am creating an instrumental track I work on it a couple bars at a time, re-creating everything I can hear. I create an audio track and I have the actual song right within Cubase so I don't have to keep referencing youtube. Sometimes its hard to hear the bass part clearly. What i do to overcome that is I create an audio track beneath the track that has the original song and I copy the sang to the new track. And then I pitch shift he new file an octave up (+12). What that does is it makes the bass pop out. . So I reference the pitch shifted track for the bass and the original track for everything else.