the G7 chord triad
Playing with the left hand
This triad is still played from the C position, but it's a stretch. It is comprised of the notes B-F-G. So to play it with your left hand, your arm doesn't move left but instead you stretch your pinky finger out from the C key to the B key. The other fingers stay in place to play the other two notes with the index finger and thumb on the F and G keys respectively.
Here's what it looks like on the staff. Those who are observant will notice that the interval counts between subsequent notes are 6 and 2. Way back in the lesson "Playing intervals and chords from the C position", it was stated that a simple two-note chord with an interval count of 6 was not so pleasant to hear. But here is a case where by adding on the top note G, it sounds pretty good. Try playing these two chords, B-F and B-F-G, and see what you think yourself.
Next, are a couple of tunes that will give your left hand a chance to practice playing the chord as well as the C Major chord. First, just play these two chords alternatively until you feel comfortable switching between them. As usual, next play just the right hand part on the treble staff until that feels comfortable. Now before you fall asleep in all that comfort, play the tune with both hands very slowly before picking up the tempo.
You may be wondering why a chord comprised of B-F-G is called a G7. Having seen that C-E-G is named C Major, you might have assumed that a chord name would be based on the lowest note on the scale. Here's a case where it is not, else it would be called a B7. And what is that "7" all about? This is just one example of why chord naming is so complicated. Lest we get side-tracked from the main goal, this topic is covered as a separate topic here. However, it is recommended that at some point you dive into this lesson in order to understand how it works as there are more unexpected chord names like this one to come.