[coliveira]

The explanation is that a seventh chord is defined as a set of third intervals. So it cannot jump from C# to F, it needs to go from C# to E#. Even though these tones are the same, the C# to F doesn't make sense. The same can be said about F G#, it doesn't make sense because it is not a third.

[thaumasiotes]

I transcribed the music on the ghost ship in Monkey Island 1, which features a lot of chords in the background involving fourths, fifths, and whatever we want to call the half-step in between fa and so.

Working with a MIDI file and without much grounding in music theory, I had and have no real way of determining whether to represent notes flat or sharp. I consulted several people and generally got a response of "Oh, interesting stuff! It's not clear how you should transcribe that."

I'm still interested in opinions! If you want to check it out, the score is here: https://musescore.com/user/36584999/scores/7810499

[acjohnson55]

The note between fa and sol is fi or se, depending on if it's the sharp 4 or flat 5 functionally. Sharp 4 would be most common, since it comes up as the leading tone of the dominant's key, e.g. in an secondary dominant, like V7/V.

But I guess you could get the flat 5 if you did the tritone substitution of the secondary dominant of the IV, which would be bV7.

[thaumasiotes]

I know that fa sharp is fi and so flat is se. The point of my comment was (1) that I was having difficulty labeling the note in question, meaning I couldn't use either name; and (2) that the heuristic "use the enharmonic that doesn't interfere with other nearby notes" doesn't work, because the notes a half-step away in either direction are both in use.

[acjohnson55]

Oh sorry, I misread your comment and that you were referring to a specific piece. Are you talking about the vibraphone part in the beginning? If so, I think you did it right. I wouldn't consider those little dips of the top note to be a chord change, but just a neighbor tone (https://en.wikipedia.org/wiki/Nonchord_tone#Neighbor_tone). So I'd treat it melodically and just put it on the adjacent line, with whatever accidental works. Like you did!

And then I think you may be talking specifically about measure 11. I'm pretty rusty on my analysis, but it seems like it's the iv7 chord, but starting and ending with a chromatically raised root, which is slick because it acts as a passing tone from the i chord in measure 10 and the V in measure 13. I would probably do Gb -> F -> Gb, because the F is the chord tone, and the Gb is the nonchord ornament. But yeah, probably doesn't really matter!

[Kye]

My understanding is flat vs sharp is largely about intended use. Something about some instruments makes one way or the other better for playing.

[thaumasiotes]

I've seen a few theories in various places:

- Match the type of accidentals used by the key signature.

- Use sharps when the melody is moving up, and flats when it's moving down.

- Use whatever accidentals give you a visually pleasing spacing of notes in "thirds" as represented on the staff. (As advocated here.)

- Use the accidentals that are physically compatible with other notes in the chord. (Only a concern for certain instruments, but e.g. I understand that the pedals on a harp affect many strings at once, so playing a particular combination of notes may require a clever approach to the pedals, indicated by what might otherwise look like an unnatural set of accidentals. This wouldn't apply to a piano, where G# is just a separate key from G, not a modification of the G key.) I think this is what you're going for?

[skybrian]

Another example would be the bass side of an accordion where Db and C# imply different buttons (though not different sounds - there are duplicates) and they’re quite far away from each other.

[coliveira]

The accident you use really depends on the context. If you're talking about chords, then you should follow the "stack of thirds" explanation that I gave above, it is how chord theory works. However, the other rules you mention also can be used depending on your situation. In a melody, you normally want to add accidents only when needed.