The triphonic replaces the extended tone with the genus chord
The variation of the seventh chord is a fainter scale that addresses (basically as you'd expect so far) four degrees up to the target chord. They can be viewed from two angles: the D-7 is connected to the G7alt, or the D-7 is connected to the D711♭♯(Libyan seven).
Sometimes students use a triplet instead, but to make it more effective, they change its extended tone. It is feasible to make extended changes to a genus seven chords that are three full tones apart (as long as they do not conflict with melodic tones), but usually this loses the significance of using triplet substitutions, because after changing D7♭it sounds more like the G7 chords that have not changed the extended tone. Of course, it's okay to do so, but it doesn't add tension to the chord tone—it's the opposite.
A trilogy-amphotonic alternative chord generally uses a natural extension tone (because we are essentially out of tune to a chord that is three full tones apart acoustically, and the natural extension tone reinforces this out-of-tune feel). Or more simply, the natural extension of a genus seven chord with a distance of three full tones is the same as the variation extension tone on the original genus seven chords.
Using a natural extension of a genus seven chord that is three full tones apart is equivalent to changing the original genus seven chords to a variation of the genus seven chords, which is the usual change in the extension tones in the genus chords. For example, the natural nine tones on the genus chords are guided to the descending nine tones, and then to the five notes on the chords to be solved by the genus chords. The thirteen tones of the genus chords are guided to thirteen notes, and finally solve to the natural nine tones on the target chord.
There is no doubt that many of you already know this knowledge about the tritone. To reiterate, the problem is the difference between "knowing" and "using". Let's examine the tritonic substitution in the context of music.
Often, when students hear the term tritonic substitution, they think it means changing ii-V to ii-II7 ♭(sometimes called substitution V7). This is one of the uses of tritonic substitution (an important one), but it is also the least dramatic use of ordinary ii-V changes.
Examples of songs
When you find that there is a suitable place in the music to use the triphotosic substitution, especially (according to the melody) can use the entire distance of the triphoto of the two-v, it can produce a surprising and dramatic harmonic effect, but also retain the function of ii-V. A famous example is the song "All the Things You Are". Let's take a look at the first four bars of the usual harmony proceeds:
Let's take a look at the three-tone substitution that is generally used in the third stanza:
In this example, the usual chord in the third bar is E7♭. If you add the associated second-level chord of E7♭, it is B-7♭. As you can see, the above substitution is carried out by an ii-V of the three full tones, that is, E-7 to A7.
I've always enjoyed using this three-tone substitution in the second half of the A-part of "My Romance". Again, let's first look at the usual harmonic progression of the piece:
Then there is the notation example using the triphratonic substitution:
In the fourth subsection above, the usual chords are F-7 through B7♭, which is an ii-V chord of iv magnitude connected to the beginning of the B segment. I replaced the entire ii-V, i.e., ii-7 and V7 chords, using an ii-V that was three full tones away from them. Doing so makes the effect of these triphalistal substitutions dramatic: a temporary sense of out-of-tune, or a pleasant but wrong chord progression, but this progression still has a harmonic significance.