noun
title song; title track
Wasei-eigo from English 'title tune'; refers to the main song of a record or album, often sharing the album's name.
wasei-eigo (Japanese-coined English), from title tune
このアルバムのタイトルチューンはとてもキャッチーだ。
The title track of this album is very catchy.
ライブの最後にタイトルチューンを演奏した。
They performed the title song at the end of the concert.
Variant with interpunct; less common in everyday writing.
主題歌 is a broader term for theme song (e.g., of a TV show or movie), while タイトルチューン specifically refers to the title track of a music album.
Wasei-eigo from English 'title tune'. It is wasei.