How do i fix instruments in a song?

[David Ingram]

Hi list members, i have a song that i conpleted but when i wint back to listen to it, it sounded different. I noticed that the bass patch didn’t sound anything like what i recorded and the electric piano patch seemed to not exist at all. I’d like to know if there is anything that i can do to change the tracks mentioned back to what i recorded originally? Thank you for any information that you might have concerning this question.