Chord Names Font Size

[Kamal]

How do you change the default font size of chord names?

I have tried the following but it didn't work:

  \chords {
    \set fontSize = #-2
    e2.:m e:m e:m b:7 b:7
    b:7 b:7 e:m g d
}
\version "2.6.5

Thank you.