Other scales are used, but they are based on the keys of D and G major. There are 8 scales that form the basis of most Irish dance music:

Scales based on Dmajor:
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D major/D Ionian: D E F# G A B C# d
E Dorian:            E F# G A B C# d e
A Mixolydian:                  A B C# d e f# g a
B Natural minor/Aeolian:          B C# d e f# g a b

Scales based on Gmajor:
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G major/G Ionian: G A B C D E F# g
A Dorian:            A B C D E F# g a
D Mixolydian:                D E F# g a b c d
E Natural minor/Aeolian:         E F# g a b c d e

S. in Seattle