How to map 2 audio streams?

I’m trying to map 2 audio streams with dshow and 1 video stream with gdigrap into my output. The first audio is system sound: “Stereo Mix (Realtek Audio)”. The second audio is my Behringer audio interface: “IN 1-2 (BEHRINGER UMC 202HD 192k)”. Here is my command line:

ffmpeg -f dshow -i audio=”Stereo Mix (Realtek Audio)” ^
-f dshow -i audio=”IN 1-2 (BEHRINGER UMC 202HD 192k)” ^
-f gdigrab -framerate 30 -i title=”TEST7″ ^
-map 0:a:0 -map 1:a:1 -map 2:v output7.asf

I’m not understanding how the arguments work, specifically the “::stream” part. I thought this would put the first audio into the the first “stream” (::0) the second audio in to the second stream (::1) along with the video.

I get this error:

Stream map ‘1:a:1’ matches no streams.
To ignore this, add a trailing ‘?’ to the map.

When I change to this: -map 0:a:0 -map 1:a:1? -map 2:v output7.asf

I get no audio from my Behringer interface.

No matter what I try, I only get the first audio stream – changing order will give me audio from the Behringer interface, and no system sound, for example.

Can someone help me straighten out my mappings?