diff --git a/lib/appointment.rb b/lib/appointment.rb
index e69de29bb2..f24404e566 100644
--- a/lib/appointment.rb
+++ b/lib/appointment.rb
@@ -0,0 +1,17 @@
+class Appointment
+
+  attr_accessor :date, :patient, :doctor
+
+  @@all = []
+
+  def initialize(date, patient, doctor)
+    @date = date
+    @patient = patient
+    @doctor = doctor
+    @@all << self
+  end
+
+  def self.all
+    @@all
+  end
+end
diff --git a/lib/artist.rb b/lib/artist.rb
index e69de29bb2..dce8ae0669 100644
--- a/lib/artist.rb
+++ b/lib/artist.rb
@@ -0,0 +1,33 @@
+class Artist
+
+  attr_accessor :name
+
+  @@all = []
+
+  def initialize(name)
+    @name = name
+    @@all <<  self
+  end
+
+  def self.all
+    @@all
+  end
+
+  def songs
+    Song.all.select{|song| song.artist == self}
+  end
+
+  def new_song(name, genre)
+    song = Song.new(name, self, genre)
+  end
+
+  def genres
+    artist_genres = []
+    Song.all.each do |song|
+      if song.artist == self
+        artist_genres << song.genre
+      end
+    end
+    artist_genres
+  end
+end
diff --git a/lib/doctor.rb b/lib/doctor.rb
index e69de29bb2..a7107b9683 100644
--- a/lib/doctor.rb
+++ b/lib/doctor.rb
@@ -0,0 +1,32 @@
+class Doctor
+  @@all = []
+  attr_accessor :name
+
+  def initialize(name)
+    @name = name
+    @@all << self
+  end
+
+  def self.all
+    @@all
+  end
+
+  def appointments
+    Appointment.all.select{|appointment| appointment.doctor == self}
+  end
+
+  def new_appointment(date, patient)
+    Appointment.new(date, patient, self)
+  end
+
+  def patients
+    doctor_patients = []
+    Appointment.all.each do |appointment|
+      if appointment.doctor == self
+        doctor_patients << appointment.patient
+      end
+    end
+    doctor_patients
+  end
+
+end
diff --git a/lib/genre.rb b/lib/genre.rb
index e69de29bb2..18101281a2 100644
--- a/lib/genre.rb
+++ b/lib/genre.rb
@@ -0,0 +1,28 @@
+class Genre
+  @@all = []
+  attr_accessor :name
+
+  def initialize(name)
+    @name = name
+    @@all << self
+  end
+
+  def self.all
+    @@all
+  end
+
+  def songs
+    Song.all.select{|song| song.genre == self}
+  end
+
+  def artists
+    genre_artists = []
+    Song.all.each do |song|
+      if song.genre == self
+        genre_artists << song.artist
+      end
+    end
+    genre_artists
+  end
+
+end
diff --git a/lib/patient.rb b/lib/patient.rb
index e69de29bb2..e412515eea 100644
--- a/lib/patient.rb
+++ b/lib/patient.rb
@@ -0,0 +1,31 @@
+class Patient
+  @@all = []
+  attr_accessor :name
+
+  def initialize(name)
+    @name = name
+    @@all << self
+  end
+
+  def self.all
+    @@all
+  end
+
+  def new_appointment(date, doctor)
+    Appointment.new(date, self, doctor)
+  end
+
+  def appointments
+    Appointment.all.select{|appointment| appointment.patient == self}
+  end
+
+  def doctors
+    patient_doctors = []
+    Appointment.all.each do |appointment|
+      if appointment.patient == self
+        patient_doctors << appointment.doctor
+      end
+    end
+    patient_doctors
+  end
+end
diff --git a/lib/song.rb b/lib/song.rb
index e69de29bb2..aae58c1d6b 100644
--- a/lib/song.rb
+++ b/lib/song.rb
@@ -0,0 +1,15 @@
+class Song
+  @@all = []
+  attr_accessor :name, :artist, :genre
+
+  def initialize(name, artist, genre)
+    @name = name
+    @artist = artist
+    @genre = genre
+    @@all << self
+  end
+
+  def self.all
+    @@all
+  end
+end