i'm guessing that the Sony mic is a ribbon or condenser of some sort? Whatever it is try using the SM57 for the vocal/tenor and the Sony for the piano. The extra 57 can be used as an ambient mic. It's not very suitable but it'll do since you don't have fx on your MD recorder. Or you could try the 57 on the piano and the Sony as an ambient mic. I think the former is better. Also try to position the tenor as far as possible from the piano. You should close mic the piano and let the ambient mic(hopefully) pick up the ambient piano sound. To make the sound big, you could always bounce it different tracks and layer them on the multitrack. Hope this helps.