rework validations in Musician so that the opposite works (true, too)
rework validations in Part so that the opposite works (true, too)
add spacing to associations and validations in classes
make sure name of musician is capitalized before it is created
make sure instrument input is downcased before it is created
make sure title input is downcased for Piece before it is created
remove letter only validation for piece titles (pieces can have numbers and symbols, too...)
make sure name of composer is capitalized before it is created
make sure instrument is downcased before it is created, in Part