Singing During Distribution of Ashes

[sr.christinaosf]

 

I am a bit confused as to how the singing is to proceed during ash distribution.
The people could all chant the given antiphons on a straight tone, or someone could cantor them (as in the responsorial psalm). The microphone we use, however, is on the ambo. 
Does anyone know if it is permissible to use the ambo for this situation as I know there are directives limiting its use.
Any other thoughts or suggestions would be appreciated.