G-flat major
"Connect" is a J-pop song with instrumentation from piano, violin, acoustic guitar, electric guitar, drums, and a synthesizer. According to a book of sheet music published by Shinko Music Entertainment, it is set in common time and moves at a tempo of 175 beats per minute. Beginning in the D minor key, the introduction starts with only piano accompanying ClariS' vocals in the chorus melody. A bridge is used in G-flat major with added drums and violin to transition into the first verse in C minor, which shifts back to G-flat major with the chorus. After another bridge, still in G-flat major, this pattern is repeated for the second verse and chorus featuring the same music with different lyrics. The second key shift from C minor to G-flat major is the final key change of the song. A break is used to transition into a short third verse, followed by the chorus as the outro. A coda is used to close the song.