For instance, there is a song with
1) Bass played by member1
and
2) Drums played by member2
In this setup, the song can not have a major or minor key information _yet_, and will be determined by a guitarist or keyboardist, or any other member3.
Bass player, for example, knows that he played in G, but did not define the mood of the song. After a guitar player (member3) plays his part, the song can turn to be in Gmajor _OR_ in Gminor.
Or both(!) -- in different remixes.
You can say: oh, just use your ears or tuner then to define the notes that were played!
Okay, but what if the main/first/last (not root!) bass note, of the track example above is in G, but the song is actually in some variant of C, also yet undefined? That can easily happen, be valid, and make a beautiful track/song afterwards.
In this case, although a bassline does not state it by itself, bassist can provide the info for further remixers that the song is actually in G.
Which [scale of] G though -- to be defined by next creative person.
Edited by
wishnewsky on November 26 2020 03:00
https://www.youtube.com/channel/UC73JG5IfzJ45osSRp5Kbpbg?sub_confirmation=1