Aha! in a Little Black Box.
You play a note, and it automatically senses what note you're trying to play and tells you if you're flat or sharp. It lets you know firmly how the note varies as you strike it. I didn't realize a note changes pitch just as you strike it, or lowers slightly if you hit it a different way. I didn't realize alot of things. Our relationship is based entirely on insight.
She's simple to use. You just set it down right next to you, powers off a few batteries and lasts forever. She is all about frequency. She's colorless.
I guess you could say I'm in lurve...