열기 (Heat) is the fourth track from the mini-album + + by LOONA. It was later included in the repackage album X X as the nineth track.
‘열기’, is a track that proves a point that even without aggressive tempo, the temperature of the music can become heated up by the fervor of the girls.
- Vocals Directed by: G-high (MonoTree)
- Digital Editing by: Chang Woo Young
- Recorded by: Min Seong Soo @doobdoob Studio, G-high @MonoTree Studio
- Mixed by: Hwang Hyun @MonoTree Studio
- The Korean title, "Yeolgi", directly translates to "Heat".
- The track was named "열기 (9)", pronounced as "Yeolgi (Gu)". It translates to "Hot Air Balloon"
- "Hot Air Balloon" - the song is about flying higher up with someone.
- "Bung bung" is an onomatopoeia for the sound a hot air balloon makes.
- 콜록콜록 (kollok kollok) is an onomatopoeia for the sound coughing makes (ex. coughs when you have a cold). Coughs can be heard in the song after that line.
- Brooke Toia also participated in the production of "new".
- Daniel Caesar and Ludwig Lindell also participated in the production of "new" and "Singing in the Rain".
- The song was originally titled "Weekend".
- The original publishers were The Kennel AB and Eccentric Music AS.
- The sub-publisher was Universal Music Publishing Korea.