To match The Grand with the tuning of accompaniment instruments or recordings, use the Master Tune control. The control range is from 415.3Hz to 466.2Hz, which equals -100 cents to +100 cents. The default value is 440Hz, which in The Grand corresponds to A3 and is the commonly used pitch for tuning.
The default tuning of The Grand is the tuning the pianos have originally been recorded with. This is a “stretched tuning”, i.e. in order to compensate for the inharmonicity of the piano strings, the upper notes are tuned increasingly higher and the lower notes are tuned increasingly lower. For the most genuine sound of the piano, leave the tuning as it is. By deactivating the Stretched Tuning button you can apply an equal temperament. This can be necessary when you want to layer the piano with other sounds that come with a pure equal temperament.
Additionally, The Grand comes with many ready-to-use tuning scale presets, e.g. historical tuning scales in different keys like the Werckmeister, Kirnberger, and other scales.