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. 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.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.