"L86" is a tense piece in 4/4. Much like the area it was composed for, it has a digital sound. It is based on rising major sevenths that create a sharp dissonance. It alternates between even rhythm in crotchets and syncopation, which is the source of the contrast. After its introduction, it is joined by a bassline. Nearing the end of the melody, the pulsation accelerates and the pitch moves up chromatically, which adds to its unnerving character. This repeats, now played by scarce strings and brass. A distinct middle section can be heard, as it uses sharps more frequently and forms an F-sharp major chord. Several more dissonant chords follow up, replacing the rising sevenths with less spread out passages. In a final eerie descent, the digital sounds play a shortened version of the melody and end in a trill. The track then loops.
The "86" in the name is a form ofgoroawase, aJapanese wordplay where the names of numbers are used to represent another phrase. In this case, it means "haru", howHAL Laboratory's name is said in Japanese. Combined with how Japanese substitutes the 'L'-sound for an 'R'-sound, the name of theme may be a play on the word "error".