Addressing 23017/4051 using I2C Serial Interface & PROGMEM

To Hex, or not to hex?.... [table A or table B][c or d]
An alternative conversion process

A shortcut to manually convert a binary number into its two's complement is to start at the least significant bit (LSB), and copy all the zeros (working from LSB toward the most significant bit) until the first 1 is reached; then copy that 1, and flip all the remaining bits. This shortcut allows a person to convert a number to its two's complement without first forming its ones' complement. For example: the two's complement of "0011 1100" is "1100 0100", where the underlined digits were unchanged by the copying operation (while the rest of the digits were flipped).
In computer circuitry, this method is no faster than the "complement and add one" method; both methods require working sequentially from right to left, propagating logic changes. The method of complementing and adding one can be sped up by a standard carry look-ahead adder circuit; the alternative method can be sped up by a similar logic transformation.

source: Two's complement - Wikipedia
defining the LED and Note bits like so:

if(midiNote == 64) ledBits |= 0x1;
if(midiNote == 65) ledBits |= 0x2;
if(midiNote == 66) ledBits |= 0x4;
if(midiNote == 67) ledBits |= 0x8;
if(midiNote == 68) ledBits |= 0x10;

the same goes for turning the LED off:-

if(midiNote == 64) ledBits &= ~0x1;
if(midiNote == 65) ledBits &= ~0x2;
if(midiNote == 66) ledBits &= ~0x4;
if(midiNote == 67) ledBits &= ~0x8;
if(midiNote == 68) ledBits &= ~0x10;