I play clarinet in the treble clef. I cannot read bass clef. A friend told me that if I have a score in bass clef, I could alter the key and play it as a treble clef piece. Is that true ? it doesn't make sense to me.
If the piece is in the key of C major, for example, in the bass clef, you can add three sharps to the key signature, pretend it's written in the treble clef, and play it transposed to A major. Or you can add four flats, pretend it's written in the treble clef, and play it in Ab major. This works because any bass-clef note is an octave and a sixth below the corresponding note (placement, that is) on the treble clef.