noun
Ionian mode
A musical mode equivalent to the modern major scale. Used in Western music theory contexts.
イオニア旋法は長調の基礎となる音階です。
The Ionian mode is the scale that forms the basis of the major key.
長音階 is the general term for a major scale, while イオニア旋法 specifically refers to the Ionian mode in modal theory.
From English 'Ionian mode', referring to the ancient Greek mode associated with Ionia, adopted in medieval and modern Western music theory.