play :: Float -- ^ Frequency
     -> Float -- ^ Duration
     -> Z80ASM
play f duration = do
  ld HL $ pitchCode f
  ld DE . round $ f * duration
  call BEEPER
play :: Float -- ^ Frequency
     -> Float -- ^ Duration
     -> Z80ASM
play f duration = do
  ld HL $ pitchCode f
  ld DE . round $ f * duration
  call BEEPER
play f duration = do
  ld HL $ pitchCode f
  ld DE . round $ f * duration
  call BEEPER