Does this passage have a lydian sound?

Question

The music sources is Album national russe (Köhler, Louis), and the particular passage is...

...before saying the music is in G major and there isn't any C# to make lydian, hear me out. The basic voice leading for I6 IV would have voice leading of ^5 ^6, and if the line to the ^6 was a descent it would use a lowered seventh, like these...

If the lowered seventh version were tonicized to C the line would become ^5 ^4 ^3. So, the point I'm getting at is the ^7 is raised rather than the typical lowered. It's even emphasized as an accented passing tone. The F# is played above a bass/root C for an augmented fourth.

I would think from a jazz perspective that C chord would be labelled not as plain Csus4 but something like C(#4). Of course the style of this music isn't jazz, but it seems to me that augmented fourth (keep in mind it's not resolving like a dominant tritone to B-G, C is the chord root) is the source of the lydian sound. My understanding is common practice avoided that sound by lowering the ^7. The fact that it isn't lowered, and is accented, makes me think the passage could be described as having a lydian sound, lydian tonality. Even if it is for only a brief passage.

Answer 1

To complement @Dekkadeci's correct analysis ...

OP mentions a "jazz context". So let's imagine this song being played by a jazz group with a soloist improvising over the chord changes.

The expected "arrangement" of measures 9–13 would be G | C | D | G without alterations. Jazz musicians would recognize that the entire passage is in the key of G, and that the C chord is not changing the tonality. Thus, the soloist (and accompanying instruments) would play F#, not because the chord needs alteration or any reference to Lydian, but because G major has F# in it.

Certainly, heard in isolation, there is a Lydian-ish sound, but this is incidental and would not be considered analytically significant. Said another way: the measure is Lydian-ish, but the passage as a whole is not.

An equivalent question would be to ask if measure 11 has a Mixolydian sound, since there is a C natural against what is otherwise a D major chord. And in a jazz context, many musicians would use a Mixolydian scale in that measure, but analytically there's no change of mode.

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It's also worth noting that the melody itself is an elaborated, descending G major scale:

Answer 2

If you analyze the passage as if it tonicizes C major instead of remaining in G major, then you can say that the passage has a Lydian sound. F♯ does turn the C major scale into the C Lydian scale, after all.

Do note that every bar in the passage except for the highlighted Bars 9-10 and the similar Bars 13-14 make claiming that Bars 9-10 tonicize C major (the IV chord) a hard sell, as Bars 1-8 keep up a G-D double pedal on the first beats of those bars, and Bars 11-12 and Bars 15-16 can both be harmonically analyzed as V-I in G major, inversions and nonchord tones notwithstanding. Bars 15-16 cadence at a repeat and an assumed phrase ending to boot, making a sell that the passage drifts away from G major at any point even harder.