Could you pls help me with this question.

If you generate a song in BIAB, usually it only has a few tracks (bass, drum, guitar, piano, synth).

If you add your own vocal singing the melody, and some harmony vocals, it seems you still only have about 10 tracks.

But when I saw some mixing tutorials on the web, especially for the professional songs, apparently a song may have 60, 70 tracks.

How can you have so many tracks? Could you pls explain what tracks you should or can add after generating the song in BIAB?

My sincere thanks,