Sample in Standing Wave 3 Actionscript Library

I am trying to get my head around StandingWave 3. I can create IAudioSources and play them but I am trying to figure out how to use the Sample part.

I tried mixing an IAudioSource into a Sample by Sample.mixIn().

testSample.mixIn(mp1.getSample(mp1.frameCount)); player.play(testSample);

Any steps in the right direction will be a big help.

I got this working by using extractSound() on an mp3.

Thanks