routes.rb

Rails.application.routes.draw do

  concern :scrobbles do
    resources :scrobbles, only: [:index]
  end

  concern :users do
    resources :users, only: [:index]
  end

  concern :tracks do
    resources :tracks, only: [:index]
  end

  resources :scrobbles, only: [:index, :show]

  resources :users, only: [:index, :show], concerns: [:scrobbles, :tracks]

  constraints(id: /.+/) do
    resources :artists, only: [:index, :show], concerns: [:scrobbles, :users] do
      resources :tracks, only: [:index, :show], concerns: [:scrobbles, :users]
    end
  end

  root 'home#index'
end