diff --git a/lib/budik.rb b/lib/budik.rb
index c530308..98ae25a 100644
--- a/lib/budik.rb
+++ b/lib/budik.rb
@@ -19,7 +19,7 @@
 #require './budik/devices.rb'
 #require './budik/player.rb'
 #require './budik/rng.rb'
-#require './budik/sources.rb'
+require './lib/budik/sources'
 require './lib/budik/version'
 
 module Budik
diff --git a/lib/budik/config/lang/en.yml b/lib/budik/config/lang/en.yml
index e6bd98b..d005d98 100644
--- a/lib/budik/config/lang/en.yml
+++ b/lib/budik/config/lang/en.yml
@@ -1,3 +1,5 @@
 lang: "en" # Do not remove this line.
 config:
   example: "This is an example string."
+sources:
+  invalid_item: "Item %1 is invalid."
diff --git a/lib/budik/config/templates/sources_example.yml b/lib/budik/config/templates/sources_example.yml
new file mode 100644
index 0000000..6d7da53
--- /dev/null
+++ b/lib/budik/config/templates/sources_example.yml
@@ -0,0 +1,24 @@
+---
+- "path"
+-
+  - "path1"
+  - "path2"
+-
+  name: "name"
+  path: "path"
+-
+  name: "name"
+  category: ["category1", "subcategory1"]
+  path: "path"
+-
+  name: "name"
+  category: ["category1", "subcategory2"]
+  path: ["path1", "path2"]
+-
+  name: "name"
+  category:
+    - "category2"
+    - "subcategory1"
+  path:
+    - "path1"
+    - "path2"
diff --git a/lib/budik/sources.rb b/lib/budik/sources.rb
new file mode 100644
index 0000000..893df1b
--- /dev/null
+++ b/lib/budik/sources.rb
@@ -0,0 +1,72 @@
+module Budik
+  class Sources
+    include Singleton
+
+    def initialize
+      @sources = []
+    end
+
+    attr_accessor :sources
+
+    def apply_mods(mods)
+      modified_sources = []
+
+      @sources.each do |source|
+        add = false
+        mods[:adds].each do |mod|
+          add = true if mod == (source[:category] & mod)
+        end
+        mods[:rms].each do |mod|
+          add = false if mod == (source[:category] & mod)
+        end
+        modified_sources << source if add
+      end
+
+      @sources = modified_sources.uniq
+    end
+
+    def parse(sources, mods = nil)
+      sources.each do |item|
+        if item.is_a? Array
+          normalized_item = { name: '', category: ['default'], path: []}
+          item.each do |subitem|
+            normalized_item[:name] += (subitem + ' + ')
+            normalized_item[:path] << subitem
+          end
+          3.times { normalized_item[:name].chop! }
+        elsif item.is_a? Hash
+          normalized_item = {}
+          normalized_item[:name] = item['name']
+          normalized_item[:category] = item['category'] ? item['category'] : ['default']
+          normalized_item[:path] = item['path']
+        elsif item.is_a? String
+          normalized_item = { name: item, category: ['default'], path: item }
+        else # TODO: test
+          fail Config.instance.lang.sources.invalid_item item.to_s
+        end
+
+        @sources << normalized_item
+      end
+
+      mods = (mods.is_a? String) ? parse_mods(mods) : mods
+      apply_mods(mods) if mods
+    end
+
+    def parse_mods(mod_string)
+      parsed_mods = { adds: [], rms: [] }
+
+      mods = mod_string.split(' ')
+      mods.each do |m|
+        mod = m.split('.')
+        if mod.first == ''
+          mod.shift
+          parsed_mods[:rms] << mod
+        else
+          parsed_mods[:adds] << mod
+        end
+      end
+
+      return parsed_mods
+    end
+  end
+end
diff --git a/spec/lib/budik/sources_spec.rb b/spec/lib/budik/sources_spec.rb
new file mode 100644
index 0000000..3302fb6
--- /dev/null
+++ b/spec/lib/budik/sources_spec.rb
@@ -0,0 +1,85 @@
+#require 'r18n-core'
+require 'singleton'
+require 'spec_helper'
+require 'yaml'
+
+require 'budik/sources'
+
+describe Budik::Sources, '#apply_mods' do
+  it 'filters sources by applying modifiers' do
+    Budik::Sources.instance.parse(YAML.load_file('./lib/budik/config/templates/sources_example.yml'))
+
+    mods = {adds: [['category1']], rms: [['subcategory1']]}
+    Budik::Sources.instance.apply_mods(mods)
+    sources_expected_result = [
+        {name: 'name',
+         category: ['category1', 'subcategory2'],
+         path: ['path1', 'path2']}
+    ]
+
+    expect(Budik::Sources.instance.sources).to eq sources_expected_result
+    Budik::Sources.instance.sources = []
+  end
+end
+
+describe Budik::Sources, '#parse' do
+  context 'without modifiers' do
+    it 'parses sources to program usable format' do
+      sources_example = YAML.load_file('./lib/budik/config/templates/sources_example.yml')
+      Budik::Sources.instance.parse(sources_example)
+      sources_expected_result = [
+        {name: 'path',
+         category: ['default'],
+         path: 'path'},
+        
+         {name: 'path1 + path2',
+         category: ['default'],
+         path: ['path1', 'path2']},
+        
+        {name: 'name',
+         category: ['default'],
+         path: 'path'},
+        
+        {name: 'name',
+         category: ['category1', 'subcategory1'],
+         path: 'path'},
+        
+        {name: 'name',
+         category: ['category1', 'subcategory2'],
+         path: ['path1', 'path2']},
+        
+        {name: 'name',
+         category: ['category2', 'subcategory1'],
+         path: ['path1', 'path2']}
+      ]
+      
+      expect(Budik::Sources.instance.sources).to eq sources_expected_result
+      Budik::Sources.instance.sources = []
+     end
+  end
+
+  context 'with modifiers' do
+    it 'parses sources to program usable format' do
+      mods_example = '.subcategory1 .default category1'
+      sources_example = YAML.load_file('./lib/budik/config/templates/sources_example.yml')
+      Budik::Sources.instance.parse(sources_example, mods_example)
+      sources_expected_result = [
+         {name: 'name',
+         category: ['category1', 'subcategory2'],
+         path: ['path1', 'path2']}
+      ]
+      
+      expect(Budik::Sources.instance.sources).to eq sources_expected_result
+      Budik::Sources.instance.sources = []
+    end
+  end
+end
+
+describe Budik::Sources, '#parse_mods' do
+  it 'parses string with modifiers' do
+    parsed_mods = Budik::Sources.instance.parse_mods('a.b c.d.e .f .g.h i .j k.l .m.n.o')
+    expected_result = { adds: [['a', 'b'], ['c', 'd', 'e'], ['i'], ['k', 'l']], rms: [['f'], ['g', 'h'], ['j'], ['m', 'n', 'o']]}
+
+    expect(parsed_mods).to eq expected_result
+  end
+end