I sympathize with your loss of income due to the novel coronavirus. After sending this message, I will make a contribution to you via PayPal.

There is one issue that I would like to bring up with you. You are probably already aware of what I will point out, but your site is so large, I haven’t found a discussion of it.

The issue is illustrated by your C add9/11 chord, which you say is “valid” and “sounds fantastic”.

Of course, everyone’s ear is different, but I would say that, to sound good, this chord requires a certain voicing.

If it is voiced as 1 4 5 9 10 (C F G D’ E’, where a prime indicates that the pitch is up an octave; also 10 = 3′), then it sounds quite beautiful to me.

However, if it is voiced as 1 3 5 9 11 (C E G D’ F’), then it sounds too harsh to me.

There is a reason for the strong dissonance: the pitches E and F’ form a minor 9th interval. Play these two notes by themselves to see how harsh this interval sounds.

In jazz music theory, this type of dissonance is called an “avoid note” or a “handle-with-care note”. For instance, when soloing over a major chord, a jazz musician avoids playing the 11th, except perhaps a passing tone, because it clashes with the 3rd of the major chord. For the same reason, the Cmaj7add11 chord is rarely played; it is usually replaced by Cmaj7add#11 (C Lydian chord). In contrast, a Cm7add11 sounds beautiful, as the 11 does not clash with the b3. There are also other situations where is clash occurs, such as a 5 and a b13 played together.

One way to eliminate the dissonance is to “re-voice”, by which I mean invert the minor 9th interval, turning it into a major 7th interval. For instance, by changing the minor ninth E F’ into the major seventh F E’, the harsh chord C E G D’ F’ becomes the lovely chord C F G D’ E’.

Note, however, that there are exceptions to the rule of thumb that minor 9th intervals ought to be avoided. An example is the highly useful C7b9 chord, in which the interval from 1 to b9 is (obviously) a minor 9th. Sometimes the minor 9th dissonance has just the right sound.

I would be interested to hear what you think about this matter.

Best wishes,
Brad

Hope they help you. Let me know if you have any problems with the dimensions and I’ll work on an updated version. Reading standard notation is not necessary, however, reading the rhythmical parts is essential. You should consider getting a program like Guitar Pro and creating rhythm training tracks. I’ll do an article in the future about the importance of that.