The DSi Instrument Tuner is an application that was available for purchase on the Nintendo DSi, which also included a mini-game themed around Balloon Fight.
In the tuner mode, the top screen will show you how in-tune or out-of-tune an instrument is when you play a note. Also, the bottom screen has a small section of a keyboard, where you can play any note as a reference.
While in tuner mode, there are three styles of the interface you can choose from three themes. Type A has woodgrain and beige borders, and a more traditional display. Type B has a more "synthetic" style with a black background and green borders and an electronic display. Type C has a Game & Watch theme, with borders that are similar to a Gold-Series Game & Watch and the display has segmented number displays and even a small Mr. Game & Watch to act as the needle. The instrument also changes between themes, with a sine wave for Type A, an electric piano sound for Type B, and a square wave for Type C.
By clicking the "Game" tab at the bottom, you can play a mini-game called Tuner Fight. In the game, 20 Balloons will float upward in what appears to be a Bonus Stage, all with a note specified on them. Before the Balloons fly off-screen, the player has to play that note within a certain range in order to pop it. At the end, the player is shown their "Report Card", where it shows which notes were missed and how in-tune the instrument was when playing the note.
- While the game can no longer be purchased on an original DSi or DSi XL because of the DSi Shop closing, the game can still be purchased on any 3DS system through the eShop.
- This game was part of a set of two games, with the other one being DSi Metronome, which was a metronome with a Donkey Kong themed mini-game.