The Difference Between E Flat & B Flat Instruments

You may wonder what it means when an instrument is, for example, a B flat instrument? It means that if you play a note on a B flat instrument without any valves depressed, you will be playing selected notes from the CONCERT B flat scale. Think of a piano which is an instrument in the key of C. Play a B flat scale on the piano and you will be playing a Concert B flat scale. The C scale on a euphonium is the same as a B flat scale on a piano. Similarly, if an instrument is in the key of E flat, such as the alto horn or soprano cornet, then without any valves depressed, it would play selected notes from the CONCERT E flat scale. I'm sure there is a more precise definition but this works well for me.