The fretboard position that is used for the minor pentatonic scale will determine the key you are playing in. The first note in the pattern (on the 6th string) will indicate exactly which key the pattern is in. For example, beginning the scale on the third fret of the 6th string (a G note) means you are playing in the key of G. Beginning pattern one on the eighth fret of the 6th string (a C note) means you are playing in the key of C.