Tonal.transpose() returns scale with notes in wrong register

[heyaphra]

Working beautifully on my app in the key of C. Registral errors occurring when tranposing to other keys. Console logged some of these out:

Interval structure returned is correct.
myscale = Tonal.scale('major');
=>["1P", "2M", "3M", "4P", "5P", "6M", "7M"]

Great in the key of C.
myscale.map(Tonal.transpose('C2'));
=>["C2", "D2", "E2", "F2", "G2", "A2", "B2"]

We start to see registral problems when transposing to other keys.
myscale.map(Tonal.transpose('D2'));
=> ["D2", "E2", "F#2", "G2", "A2", "B2", "C#3"]

myscale.map(Tonal.transpose('E2'));
=> ["E2", "F#2", "G#2", "A2", "B2", "C#3", "D#3"]

etc...

Can't wait to introduce this functionality to my app! Thanks again!

[danigb]

Hi @wildcat510

Thanks for reporting! 👍

But, as far as I know, this is the expected output. For example, "D2" transposed by a "7M" is "C#3"... The same can be applied to "E2" transposed by a "6M" or a "7M". In fact, "E2 major" is exactly the scale you obtained.

Am I missing something?

Regards,
Dani

[heyaphra]

A major 7th above D2 is C#2 in the same register— otherwise, we would be missing an entire note from the first octave of the scale. C major is correct because a major 7th above C2 is B2 in the same octave. If I'm transposing a C scale (or any scale) in octave register 2 to another key, the whole scale should stay in the same octave register unless I'm using the wrong method for transposing keys. All scales should be played linearly, steps 1 through 7, not steps 1-6 and then 7 an octave higher, or 1-5 with 6 and 7 and octave higher as this leaves the scale registers disjointed and incomplete. After all, in common practice scales are played 1-2-3-4-5-6-7 in the same octave. If you want supporting audio to demonstrate I can provide.

So just like myscale.map(Tonal.transpose('C2')); produces ["C2", "D2", "E2", "F2", "G2", "A2", "B2"], a uniform linear scale played from scale degree 1 to 7, I would expect the same of other keys.

Unless I'm missing something. Is this the right way to go about transposing scales as an entire unit to a different key?

[mrjacobbloom]

The cutoff for register number is always C no matter what key you're in. C# above D2 is higher than the C that follows D2 so it's in the 3rd register. C#2 is the note below D2

[heyaphra]

So is there any way I can have scales in keys other than C laid out in a register theoretically consistent with the same way a musician would notate and play it? What is the reason for the cutoff at C if it produces scales inconsistent with common practice?

[danigb]

Hi!

Yes, I think @mrjacobbloom is right here. In western music theory we use always C as the cutoff registry.

Another way to think about it is using interval sizes. For example, 7M is 11 semitones up. That's exactly the distance from D2 to C#3 (and the distance from D2 to C#2 is 1 semitone down).

I don't understand very well your explanation, @wildcat510 but It would help to have some external references or resources.

Anyway, you can always use pitch classes (note names without octave number) to avoid this problem:

["1P", "2M", "3M", "4P", "5P", "6M", "7M"].map(Tonal.transpose("D")) // => ["D", "E", "F#", "G", "A", "B", "C#"]

And you can use Tonal.Note.props to coerce to an octave: scale.map(note => Tonal.Note.props({ oct: 2 }, note)) or, if you are sure they are all pitch classes, a simple string concatenation: scale.map(note => note + "2")

Hope it helps
Regards
Dani

[heyaphra]

Looks like I misunderstood the transpose function's application. Concatenating pitch classes works.
Thanks guys!
-Nate

[danigb]

Great! I'm going to close this issue, but feel free to reopen if something is not clear.