The partial capo does not produce a ture open tuning enless the strings are actually retuned. Instead, it provides a special effect which many guitarists find interesting. Its most pupular use is to apply the capo at the second fret from the bass side, skipping the bass string and covering strings 5-4-3. This emulates DADGAD tuning, but a step higher. Another use is to apply the capo from the treble side at the second fret, skipping the first string and covering strings 2-3-4. This forms an open A chord. There are probably other applications which can yield interesting new sounds. They’re just waiting for a creative musician to discover. Experiment and enjoy.