Roman numerals analysis

I'm studying music theory in https://www.musictheory.net I have reach a point where the roman numeral analysis is explained.

A couple of lessons later, I found the next image:

I really can't make any sense out of it. You can see the first I is F, and the second I is an A! Also, ther V7 indicated, from my undestanding should be a IV.

I though it may have something to do with inversion, but how would you inverse a single note?

I am really confused, I don't know if I just didn't understand anything about roman numeral analysis, or if there is an error in that image.

Could anyone shed any light on this matter?

• Those lessons do clearly distinguish between notes and chords - if you re-read you will see why an I can be a different note if the chord changes Jan 2, 2016 at 22:22
• Maybe I misunderstood some point, but so far I have only seen the roman numeras being used for chords, both triads and sevenths. Doesn't the numeral depend enterely on the scale being used? In C major, wouldn't be C always be I?
– Leo
Jan 2, 2016 at 22:36

The point of this lesson is not to talk about Roman Numeral analysis, but instead describe phrases and cadences. So in the context of these examples the notes played are the melody and the Roman Numerals represent the harmony similarly how we would use them in Roman Numeral analysis. The only thing that is slightly unclear about this is that the key is not labeled at the start of the Roman Numeral analysis, but can easily be deduced by the first Roman Numeral as the key signature could be F major or D minor the first chord being I confirms that it is in F major.

The melody and harmony of course are intertwine in nature with all the notes except one (the A on beat 2 of measure 2) are chord tones of the harmony. The I chord contains the notes F, A, and C, the ii chord contains the notes G, Bb, and D, the V(7) chord contains the note C, E, and G (Bb is the 7th if it's there as seen in measure 2 beat 3).

• So, the roman numerals just represents the harmony where the note in the melody it's played? Is this like simplifying the score so only the melody is displayed, leaving the rest of the notes in the harmony implycitly represented by the roman numeral?
– Leo
Jan 2, 2016 at 22:53
• Pretty much. This is almost exactly what you would see on a lead sheet except you would replace the Roman Numerals with chord symbols.
– Dom
Jan 2, 2016 at 23:00
• I see, since the roman numerals were not represented in the first score, I though that I should be able to know the roman numerals given the notes present, which really really confused me and pretty much made me think I didn't understand a single thing I have been learning so far :) Thanks a lot for the explanation!!
– Leo
Jan 2, 2016 at 23:02

That to me looks like the cadential 6/4 chord progression. That is when either the tonic chord is decorated with the subdominant chord in the second inversion or the dominant chord is decorated with a tonic chord in the second inversion. For some reason, it seems like they have omitted the notation of the passing chord.

If it helps you the proper figuring of that melody should be I-I6/4-V.