Recording some harmonica for a friend of a friend. He wants me to play on a song in Db, which means playing an F# harp, the highest key, in standard cross. So I thought maybe I'd buy a lower octave harp. The only lower octave F# harp I can find is made by Seydel. I'm not familiar with them. How are they similar to or different than Hohner Marine Band or Special 20 harps? thanks.