On December 25, 2019, the song "?←HEARTBEAT" was released by 絢瀬絵里(CV.南條愛乃), 東條 希(CV.楠田亜衣奈), 矢澤にこ(CV.徳井青空). With this song being around four minutes long, at 3:30, the duration of this song is pretty average compared to other songs. This track is safe for children and doesn't appear to contain any foul language, since the "Explicit" tag was not present in this track. There is only one song in μ's Complete BEST BOX (Chapter.12), so we believe that "?←HEARTBEAT" is a single. In terms of popularity, ?←HEARTBEAT is currently below average in popularity. The overall tone is very danceable, especially with its high energy, which produces more of a euphoric, cheerful, or happy vibe.

?←HEARTBEAT テンポ

The tempo marking of ?←HEARTBEAT by 絢瀬絵里(CV.南條愛乃), 東條 希(CV.楠田亜衣奈), 矢澤にこ(CV.徳井青空) is Moderato (at a moderate speed), since this song has a tempo of 118 テンポ. With that information, we can conclude that the song has a moderate tempo. This song can go great with walking. The time signature for this track is 4/4.

?←HEARTBEAT キー

F Major is the music key of this track. This also means that this song has a camelot key of 7B. So, the perfect camelot match for 7B would be either 7B or 8A. While, 8B can give you a low energy boost. For moderate energy boost, you would use 4B and a high energy boost can either be 9B or 2B. Though, if you want a low energy drop, you should looking for songs with either a camelot key of 7A or 6B will give you a low energy drop, 10B would be a moderate one, and 5B or 12B would be a high energy drop. Lastly, 4A allows you to change the mood.