Phones nearly always have better cameras than tablets so, if you have a phone and a tablet of similar quality, try the phone first. If you have an iPhone 5 or above or a mid/high-end Android smartphone, you should get excellent results.
If you are using the camera screen, tap the ? 
button and swipe through the tips for taking a perfect sheet music photo.
We are always ready to help at support@organumconsulting.com.