How to use irig to listen while use external mic

[Jsa123]

So if I lay down a track using my acoustic through irig hd2 and now I want to listen to that while recording me singing over that track.I am using GarageBand. I did it once and now I can’t record me singing using external mic on iPad Pro . If irig is plugged in it shuts external mic off .and if I disconnect irig external mic turns back on. Can someone help me I am very new at this.

[stockpups]

Not sure about the HD (I have iRig Duo) but you should be able to record 1 at a time. Lay down the guitar, then use a new track for vocals. Make sure the Track is for VOCALS and the INPUT is correct (1 or 2). Then Hit the Monitor (orange icon) to hear it as you sing, and make sure both tracks are active (yellow headphones).