This short book contains two essays. The first is about stringed musical instruments with frets placed to accommodate the Eagle 53 musical tuning. The strings in these instruments are tuned so that 2:3:4:6:8, 4:5:8:10:16 and 7:10:14:20:28 beatless chords are easily playable. Major and minor chords occur as well but not on every note. The second essay is about an alternative musical tuning which divides the octave into nineteen equal steps instead of the usual twelve. 19EDO stands for Nineteen Equal Divisions of the Octave. There is some theory on composition as well, composing in Eagle 53 and in 19EDO.