@endtoendpaper: Stars
Scale and chord patterns for major, natural minor, harmonic minor, and melodic minor scales.
Famous people's birthdays.
# shared model methods( callbacks, validates, scopes, associations) - instance and class
module Item
extend ActiveSupport::Concern
# instance associations, scopes, validations, callbacks, methods, private methods
included do
belongs_to :user
has_many :collaborations, as: