sin·cere

– adj.
1. free of deceit, hypocrisy, or falseness; earnest.
2. genuine; real.
3. pure; unmixed; unadulterated.
4. sound; unimpaired.

au·then·tic

–adj.
1. not false or copied; genuine; real.
2. having the origin supported by unquestionable evidence; verified.
3. entitled to acceptance or belief because of agreement with known facts or experience; reliable; trustworthy.
4. executed with all due formalities.
5. a. having a range extending from the final to the octave above.
b. consisting of a dominant harmony followed by a tonic.