Flash Chord is intended to be used by all instruments, so it wouldn't make sense to provide a guitar or piano chord shape to trumpet players or saxophone players. Also, Flash Chord is a practicing tool, not a teaching tool.
We have plans to try to develop some backing chords, but it may not be supported by all browsers.
If you'd like to help us develop this functionality, check out how you can contribute on the About page.
If you see an invalid chord, please report it on the issues page of the GitHub project.
It's a temporary limitation until we figure out how to enable key restriction along with more complex chords. It's a tricky problem. :)
I think it's related to resource caching for the audio file. I've added some tweaks to make it better, but I haven't yet figured out how to make it work perfectly.
If you see something strange, please report it on the issues page of the GitHub project.
Currently, you can't, but we'd love your help developing that functionality! Check out how you can contribute on the About page.