Some many to many relationships are a bit more complex, such as relating customers to products through invoices (for instance). Let's see how to do this in Rails using a 'has many through' relationship.
I didn't pick the best example for this video (artists and tracks), but if you imagine that songs can be covered by many artists (think "Mack the Knife" or something), it works:
class Artist < ApplicationRecord
has_many :albums
has_many :tracks, through: :albums
end
The other end of the association needs to link back:
class Track < ApplicationRecord
belongs_to :album
belongs_to :media_type
belongs_to :genre
has_and_belongs_to_many :playlists
has_many :artists, through: :album
end