Composing melodies which introduce chromaticism

Question

I'm trying to rap my head around the tune "June 9th" by Boards of Canada.

So I started here:

and attempted to work out the chords that work with the bass line. My guess was Bbsus4, Bsus2, F#, G#sus4. This would suggest the scale of F# Major, however this tune doesn't sound Major. Therefore since the first chord is the third note of the the scale I presumed that the tune belonged to the Bb Phrygian mode. I tried droning a Bb behind the bass line and I actually think that Eb sounds better. Maybe the mode is that of Eb Aeolian... what do you think?

Then if we look at the first melody that sits on the base line, this starts here:

I tried playing this melody with my chords and I ended up changing the second chord to Bsus4 instead. I now have the scale F# plus the note E so things are no longer diatonic. Not only that but the melody also contains the note A.

I then tried my chords with both this melody and the second melody, which play together here:

This time I felt the chords were perhaps: Bbm, Bsus2, F#sus2 (or F#), G#m. The second melody also introduced the note D so things are really chromatic now.

What I'm primarily interested in is how a tune like this is composed. My guess is that the four bass notes were chosen first, then the four notes: D#, C#, B, G#, giving the notes from the scale of F#. But had I then tried to compose the two melodies that sit on top of the bass line, I would have restricted myself to notes in the scale of F#. What mechanism allowed the composer to choose notes outside of this scale and still have melodies that work perfectly with the bass line?

Answer 1

As topo morto commented, the opening of the first clip is in a clear G# minor. (It might help to conceptualize that first chord as having an A# root instead of a Bb root.)

The only difference between G# natural minor and F# major is that the first has E while the latter has E#. Thus when you mention in the second clip that you hear an E, you're right! But it's actually still diatonic here, since the E is diatonic in G# natural minor.

The A that appears in the second clip is the lowered second scale degree. I didn't hear a full-blown Neapolitan chord (A major in G# minor), I just heard the A as what we call a "non-chord tone." This simply means that a melodic pitch doesn't "belong" in the chord that's being played. As long as it resolves correctly (often by step), it sounds fine, as it does here!

What I'm primarily interested in is how a tune like this is composed.

I would classify this piece as being in the "ground bass" tradition. There are several other terms for this: passacaglia, chaconne, etc., but the general point is that a composer finds a bass line and just keeps repeating this bassline, gradually adding more melodic/harmonic interest above it in other voices. Probably the most common example is Pachelbel's Canon; you'll notice that the bass is the same the whole time, and only the upper voices change.

So you're on the right track: the composers created this bassline, but they then used the key of G# minor to add voices above it. Slowly they added in some chromatic non-chord tones. Pretty much any non-chord tone is possible, but I'll give you a quick rule: A chromatic pitch should resolve by step in the direction of its alteration. Thus a pitch like A (which was lowered from A#) should resolved down by step. There are occasional exceptions to this rule, but this is a pretty sound one to get you started.

Now, here's the cool thing: you can practice this on your own! Create a quick, four-measure bassline, record it using something free like Audacity, and loop it. (You can even use this bassline if you wish.) Then play it back as you experiment with music above it. Start off in the key, and then slowly add in some chromatic tones, taking care to resolve them correctly. See what works, and see what doesn't!