An Aircheck is the stereo version of a K.K. Slider song, often sounding extremely different than the version sung by the musician himself. They are obtained after K.K.'s concerts. The aircheck keeps the same melody, but because of the instrumental differences, the two versions can sometimes sound rather unalike. Airchecks often do not contain the full song as sung by K.K. because they loop.
In all games, the player will obtain an aircheck after K.K. Slider performs. A copy can only be obtained for the first performance each week. The copy can then be inserted into a stereo to play it. In New Leaf, Happy Home Designer and New Horizons, each song has a unique album in the player which can also be placed as a decoration. In New Horizons, a different aircheck can be ordered every day from the Nook Stop for 3,200 Bells.
In New Leaf and New Horizons, airchecks can sound slightly different in quality depending on the player used. There are four versions: "Hifi" (normal), "Cheap" (radio), "Phono" (phonograph), and "Retro" (retro stereo).
In Happy Home Designer and New Horizons, villagers will sometimes sing if an aircheck is playing nearby. In New Leaf, Happy Home Designer and New Horizons, instruments played while an aircheck is on harmonize with the song's chord changes.
- Main article: Secret song
- New Horizons is the only game where airchecks are known as "airchecks". In the two earlier games, they are called "Bootlegs", and "Boots" in New Leaf.
- Many of the album covers for airchecks reference real-life albums or musicians.
- The album art for some songs actually first appeared on the e-Cards for Animal Forest e+, although some removed villagers have been changed.
- The album art is also used for the Quiz Show minigame in amiibo Festival.
- Strangely, K.K. Slider sings with a normal villager voice instead of his own when an aircheck is played in Happy Home Designer.