diff --git a/internal/common/album.go b/internal/common/album.go
new file mode 100644
index 0000000..1ce2ea7
--- /dev/null
+++ b/internal/common/album.go
@@ -0,0 +1,189 @@
+package common
+
+import (
+	"crypto/md5"
+	"fmt"
+	"io"
+	"path/filepath"
+	"slices"
+	"strings"
+	"time"
+
+	"suruatoel.xyz/mcg/internal/i18n"
+)
+
+type Album struct {
+	title        string
+	songs        []*Song
+	artists      []string
+	pathes       []string
+	dates        []string
+	length       uint64
+	lastModified time.Time
+}
+
+func NewAlbum(title string) *Album {
+	album := Album{
+		title: title,
+	}
+
+	return &album
+}
+
+func (a *Album) Title() string {
+	return a.title
+}
+
+func (a *Album) AddSong(song *Song) {
+	a.songs = append(a.songs, song)
+	a.length += song.Length()
+
+	for _, artist := range song.AlbumArtists() {
+		if !slices.Contains(a.artists, artist) {
+			a.artists = append(a.artists, artist)
+		}
+	}
+
+	if !slices.Contains(a.dates, song.Date()) {
+		a.dates = append(a.dates, song.Date())
+	}
+
+	path := filepath.Base(song.File())
+	if !slices.Contains(a.pathes, path) {
+		a.pathes = append(a.pathes, path)
+	}
+
+	if !song.LastModified().After(a.lastModified) {
+		a.lastModified = song.LastModified()
+	}
+}
+
+func (a *Album) Songs() []*Song {
+	return a.songs
+}
+
+func (a *Album) Artists() []string {
+	return a.artists
+}
+
+func (a *Album) Dates() []string {
+	return a.dates
+}
+
+func (a *Album) Length() uint64 {
+	return a.length
+}
+
+func (a *Album) LastModified() time.Time {
+	return a.lastModified
+}
+
+func (a *Album) ID() string {
+	return generateAlbumId(a.title)
+}
+
+func (a *Album) Tooltip() string {
+	artists := strings.Join(a.Artists(), ", ")
+	dates := strings.Join(a.dates, ", ")
+	minutes := a.length / 60
+	seconds := a.length - minutes*60
+	length := fmt.Sprintf(i18n.T("%d:%d minutes"), minutes, seconds)
+
+	return strings.Join(
+		[]string{
+			a.title,
+			dates,
+			artists,
+			length,
+		},
+		"\n",
+	)
+}
+
+type PlaylistAlbum struct {
+	*Album
+	songs  []*PlaylistSong
+	length uint64
+}
+
+func NewPlaylistAlbum(album *Album) *PlaylistAlbum {
+	playlistAlbum := PlaylistAlbum{
+		Album: album,
+	}
+
+	return &playlistAlbum
+}
+
+func (a *PlaylistAlbum) AddSong(playlistSong *PlaylistSong) {
+	a.songs = append(a.songs, playlistSong)
+
+	song := playlistSong.Song
+	a.length += song.Length()
+
+	for _, artist := range song.AlbumArtists() {
+		if !slices.Contains(a.artists, artist) {
+			a.artists = append(a.artists, artist)
+		}
+	}
+
+	if !slices.Contains(a.dates, song.Date()) {
+		a.dates = append(a.dates, song.Date())
+	}
+
+	path := filepath.Base(song.File())
+	if !slices.Contains(a.pathes, path) {
+		a.pathes = append(a.pathes, path)
+	}
+}
+
+func (a *PlaylistAlbum) Songs() []*PlaylistSong {
+	return a.songs
+}
+
+func (a *PlaylistAlbum) Length() uint64 {
+	return a.length
+}
+
+func (a *Album) IsMatch(query string) bool {
+	if query == "" {
+		return true
+	}
+
+	for keyword := range strings.SplitSeq(query, " ") {
+		if !a.isKeywordMatch(keyword) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func (a *Album) isKeywordMatch(keyword string) bool {
+	if strings.Contains(strings.ToLower(a.title), keyword) {
+		return true
+	}
+	for _, artist := range a.artists {
+		if strings.Contains(strings.ToLower(artist), keyword) {
+			return true
+		}
+	}
+	for _, song := range a.songs {
+		if strings.Contains(strings.ToLower(song.Title()), keyword) {
+			return true
+		}
+		if strings.Contains(strings.ToLower(song.File()), keyword) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func generateAlbumId(values ...string) string {
+	h := md5.New()
+	for _, value := range values {
+		io.WriteString(h, value)
+	}
+
+	return fmt.Sprintf("%x", h.Sum(nil))
+}
diff --git a/internal/common/outputdevice.go b/internal/common/outputdevice.go
new file mode 100644
index 0000000..df6aa49
--- /dev/null
+++ b/internal/common/outputdevice.go
@@ -0,0 +1,14 @@
+package common
+
+type OutputDevice struct {
+	ID      string
+	Name    string
+	Enabled bool
+}
+
+func NewOutputDevice(id string, name string) *OutputDevice {
+	return &OutputDevice{
+		ID:   id,
+		Name: name,
+	}
+}
diff --git a/internal/common/song.go b/internal/common/song.go
new file mode 100644
index 0000000..1b81806
--- /dev/null
+++ b/internal/common/song.go
@@ -0,0 +1,122 @@
+package common
+
+import (
+	"slices"
+	"time"
+)
+
+type Song struct {
+	artists      []string
+	title        string
+	file         string
+	albumartists []string
+	track        string
+	length       uint64
+	date         string
+	lastModified time.Time
+}
+
+func NewSong(artist string, title string, file string) *Song {
+	song := Song{
+		artists: []string{artist},
+		title:   title,
+		file:    file,
+	}
+
+	return &song
+}
+
+func (s *Song) AddArtist(artist string) {
+	s.artists = append(s.artists, artist)
+}
+
+func (s *Song) AddAlbumartist(artist string) {
+	s.albumartists = append(s.albumartists, artist)
+}
+
+func (s *Song) SongArtists() []string {
+	if len(s.albumartists) > 0 {
+		songArtists := []string{}
+		for _, artist := range s.artists {
+			if !slices.Contains(s.albumartists, artist) {
+				songArtists = append(songArtists, artist)
+			}
+		}
+
+		return songArtists
+	}
+
+	return []string{}
+}
+
+func (s *Song) AlbumArtists() []string {
+	if len(s.albumartists) > 0 {
+		return s.albumartists
+	}
+
+	return s.artists
+}
+
+func (s *Song) Title() string {
+	return s.title
+}
+
+func (s *Song) File() string {
+	return s.file
+}
+
+func (s *Song) SetTrack(track string) {
+	s.track = track
+}
+
+func (s *Song) Track() string {
+	return s.track
+}
+
+func (s *Song) SetLength(length uint64) {
+	s.length = length
+}
+
+func (s *Song) Length() uint64 {
+	return s.length
+}
+
+func (s *Song) SetDate(date string) {
+	s.date = date
+}
+
+func (s *Song) Date() string {
+	return s.date
+}
+
+func (s *Song) SetLastModified(lastModified time.Time) {
+	s.lastModified = lastModified
+}
+
+func (s *Song) LastModified() time.Time {
+	return s.lastModified
+}
+
+type PlaylistSong struct {
+	*Song
+	id  string
+	pos uint64
+}
+
+func NewPlaylistSong(song *Song, id string, pos uint64) *PlaylistSong {
+	playlistSong := &PlaylistSong{
+		Song: song,
+		id:   id,
+		pos:  pos,
+	}
+
+	return playlistSong
+}
+
+func (t *PlaylistSong) ID() string {
+	return t.id
+}
+
+func (t *PlaylistSong) Pos() uint64 {
+	return t.pos
+}
diff --git a/internal/common/sort.go b/internal/common/sort.go
new file mode 100644
index 0000000..7c62117
--- /dev/null
+++ b/internal/common/sort.go
@@ -0,0 +1,89 @@
+package common
+
+import "sort"
+
+type albumLessFunc func(p1, p2 *Album) bool
+
+type albumSorter struct {
+	albums []*Album
+	less   []albumLessFunc
+}
+
+func (s *albumSorter) Len() int {
+	return len(s.albums)
+}
+
+func (s *albumSorter) Swap(i, j int) {
+	s.albums[i], s.albums[j] = s.albums[j], s.albums[i]
+}
+
+func (s *albumSorter) Less(i, j int) bool {
+	p, q := s.albums[i], s.albums[j]
+
+	var k int
+	for k = 0; k < len(s.less)-1; k++ {
+		less := s.less[k]
+		switch {
+		case less(p, q):
+			return true
+		case less(q, p):
+			return false
+		}
+	}
+
+	return s.less[k](p, q)
+}
+
+func (s *albumSorter) Sort(albums []*Album) {
+	s.albums = albums
+	sort.Sort(s)
+}
+
+func OrderAlbumBy(less ...albumLessFunc) *albumSorter {
+	return &albumSorter{
+		less: less,
+	}
+}
+
+func SortAlbums(album []*Album, field string) {
+	title := orderAlbumByTitle
+	artists := orderAlbumByArtists
+	years := orderAlbumByYears
+	modified := orderAlbumByModified
+
+	var sorter *albumSorter
+	switch field {
+	case "artist":
+		sorter = OrderAlbumBy(artists, title, years, modified)
+	case "year":
+		sorter = OrderAlbumBy(years, title, artists, modified)
+	case "modified":
+		sorter = OrderAlbumBy(modified, title, artists, years)
+	default:
+		sorter = OrderAlbumBy(title, artists, years, modified)
+	}
+
+	sorter.Sort(album)
+}
+
+func orderAlbumByTitle(c1, c2 *Album) bool {
+	return c1.Title() < c2.Title()
+}
+
+func orderAlbumByArtists(left, right *Album) bool {
+	if len(left.Artists()) > 0 && len(right.Artists()) > 0 {
+		return left.Artists()[0] < right.Artists()[0]
+	}
+	return false
+}
+
+func orderAlbumByYears(c1, c2 *Album) bool {
+	if len(c1.Dates()) > 0 && len(c2.Dates()) > 0 {
+		return c1.Dates()[0] < c2.Dates()[0]
+	}
+	return false
+}
+
+func orderAlbumByModified(c1, c2 *Album) bool {
+	return c1.LastModified().Before(c2.LastModified())
+}