Schoenberg's counterpoint book.

This is probably a long shot but I've been trying to figure out section 83 of this book for what feels like forever. I can't wrap my head around why the single voice examples given express the key by themselves while examples given in the previous section require two voices to do the same. I mean, I can see why the key is pretty clear from the single voice examples, I just don't see why it isn't clear with any voice by itself in the two voice examples.

For anyone not familiar with the book, I can attach one example of each and maybe that will be enough to help one of you to help me.

one voice.pdf

two voices.pdf

Not sure I understand your question... The key could only be one of two things based on the key signature - in your examples those are obviously C or its relative minor - A.

True, the upper voice in your 2nd example could quite easily be in A minor, but the lower voice can't really because of the implied IV-V-I progression in C major.

Not sure if that helps... I'm not 100% sure why this particularly bothers you - a lot of single line passages in tonal music suggest more than one key at any one time. That's often what makes it interesting - to eventually find out that the composer's harmonisation was not you expected but works nevertheless.

Am I making sense?

Not sure I understand your question... The key could only be one of two things based on the key signature - in your examples those are obviously C or its relative minor - A.

True, the upper voice in your 2nd example could quite easily be in A minor, but the lower voice can't really because of the implied IV-V-I progression in C major.

Not sure if that helps... I'm not 100% sure why this particularly bothers you - a lot of single line passages in tonal music suggest more than one key at any one time. That's often what makes it interesting - to eventually find out that the composer's harmonisation was not you expected but works nevertheless.

Am I making sense?

The chapter I'm on is explaining how to make the key obvious with only one or two voices. Both of the examples I uploaded are supposed to concretely show the key of C major. I understand how the key is obvious, but I don't understand why you need both voices in the two voice example to make the key clear. It's bothering me because he listed a few two voice examples and then said something like, "Some lines define the key so clearly by themselves that a second voice is unnecessary," but the examples he gives for that aren't any clearer than any one line from the two voice examples. I can see the key being expressed, I just feel like I'm missing something because he makes a point to differentiate the two sets of examples.

Does the chapter have to do with modes, tonal centers, or something else?

Does the chapter have to do with modes, tonal centers, or something else?

Major and minor cadences in two voices. There's nothing about modulations yet and he makes a point of saying that modes aren't useful in an earlier chapter.