1 3 5 b7
On C7:
For a dominant chord, the 3 stays major and the 7 is lowered.
So here, 1 3 5 b7 means:
- 1
- major 3
- 5
- b 7
Compared with Cmaj7, the seventh is lowered:
A very common resolution is:
That pull toward resolution is what makes the dominant sound so important.