Similar to suspended chords, seventh chords will also appear like modified versions of chords you already know, where often only one note has been changed. For example, A7 is nearly identical to A, but removes the middle note from the pattern. Others are not this simple, such as D7, which is more like a regular D shape flipped backwards.
Practice the following chord progressions:
E7 to A
A7 to D
D7 to G
G7 to C
C7 to F
B7 to E
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