Just an update. I have tried about 10 other android emus with Smule Sing and YouWave is the only one that records someone doing a duet in correct time. The others all have problems with syncing. They may be in sync at the start but by the end, the timing has drifted. There are a few other niggles with YouWave, but it is usable now and the best performing app for quality of recording. If anyone else is having probs, let me know, I may be able to help.