I think Happy Birthday is a fine first song to learn on the ergordica. Every body knows it, it’s easy, and you might just find a few opportunities to play it. The above recording is a duet between two tenor acoustic ergordicas. One plays the melody and the other plays the chords rhythmically. The sheet music is below.
If you’re just getting started on the ergordica, I suggest learning the melody first. If you’d like, you can use the recording of the chords below to play along with. The song is in 3/4 time and in the key of G, so keep an eye out for that F#. One quick fingering tip is, when jumping from the low D to the high D, use your middle finger for the low D then ring finger for the high D. This makes it easier to get a smooth transition.
Next, you could learn the chords, and play along with the melody in the recording below. The chords sound better if you only play them on the lower row of ergordica keys. These are of course inversions from the standard chords, which isn’t ideal, but sounds better than playing the correct chords at a higher pitch.