An intonation training device for training musicians in just intonation. As disclosed, the device is a pocket-sized portable device with an audio output and a user interface which includes an LCD display and a device such as a push button for selecting an item from a menu. When the device is turned on, the LCD display indicates a key and the device emits a sustained pure chord in the key. In a preferred embodiment, the pure chord is a perfect fifth in the just scale for the key. To train his or her intonation, the user then plays a sequence of notes in the key, adjusting his or her intonation while playing to eliminate beats between the note being played and the chord being emitted by the training device. In other embodiments, the device may emit a third in the just scale for the key. The user can use the menu item selection device to select another key and the training device then continuously emits the chord in the just scale for that key. The selected key appears in the LCD display.The user interface permits specification of many modifications of the chord emitted by the training device. The chord may be augmented or diminished, major or minor, may include additional intervals, may have timbres ranging from dark to bright, may be sounded in one of a number of octaves, and may be calibrated to a number of different concert “A”s. The modifications are selected from lists and the currently-selected modification is visible in the LCD.Implementations disclosed include an implementation that employs stored samples of the chords, an implementation in which the chords are generated from waveforms, and an implementation in a portable pocket-sized multimedia asset player.