A major sixth chord is composed using a root/1st, major 3rd, perfect 5th and major 6th (or R/1-3-5-6) intervals played simultaneously. Generally written as C6 or Cma6, it is good practice to simply use an uppercase C followed by a super scripted 6 to represent it in writing (ie: C6).
Major sixth chord profile
|Intervals||root/1st, major 3rd, perfect 5th, major 6th or R/1-3-5-6|
|Common names (examples in C)||C6, Cma6, Cadd6|
|Major sixth chord voicing #2|