Background SayDigits()?

Is it possible to background SayDigits() like Background() can?

You could background the digit recording. They are in /var/lib/asterisk/sounds/digits IE:

Background(digits/20)

so how do you background the equivalent of

exten => _X.,n,SayDigits(${EXTEN:1}) ?

or

exten => s,n,SayDigits(${CALLERID(number)})) ?

Not sure. But you could make Festival generate a recording from the variable and then background that file.