Allison
I have a lovely Lachenal Edeophone English concertina c1905 with metal ends.
Every time someone says that it sounds beautiful (which is often - on Saturday at the Whittlesey Straw Bear Festival, for instance!) I think how lucky I am - I can play it for morris (the metal ends mean that it has a "bright" sound), it is a joy at sessions (where it is heard even when the melodeons are in town!) and I can accompany myself when I am singing (in any key I am good enough to play in!), as it contrasts with my deeper voice tones ... But I am still learning ...
However, as other people have said before, you have to decide what you are wanting to do and stick at it! Oh and, of course, you need to practice, practice, practice ...
"Playing and singing ...!"
Alan