[Question] Could you generalize the seven "notes" of music to four?

Hey, so I was wondering whether could you generalize the 7 notes/majors (I'm not much acquainted with music theory, so I'll refer to the term as Note) of music ie., do re mi fa sol la si, to say, four?

Lets say I want to interpret music/tone with 4 variables instead of 7 per major/strings.