I'm looking for a patch that does this:

It should be very a easy build, but I'm not quite fluent enough in musical theory to be able to rattle off the numbers. Has anyone else made this or encountered it before?

You need to create an algorithm that will give you notes of a scale, then all you need is an offset, if you want to use Lydian, Dorian etc.
The major scale is quite easy, I've done this with a class major_scale_algo.pd. Don't know if this helps...
There's a bit [pd durations] that isn't finished, if you feel like improving it, please let me know

For a minor scale, it depends on what kind of minor you want, natural, harmonic or melodic? Haven't fiddled with that, but it should follow the same approach, more or less...

@LiamG maybe a starting point:
https://github.com/patricksebastien/mtl/blob/master/closestNote-help.pd

Cheers~

Thanks for the recommendations.

I ended up borrowing the arrays used in @Hamster's excellent Cave of Creation patch and modifying it to suit my needs. I hope that It's possible that there are mistakes though--I wouln't know a Locrian from a Mixolydian!

Here's the patch: scaler.zip

[scaler-v] does the same thing but with Vanilla friendly objects.

One day I hope to make a version that coverers (some of the) Indian raags. Apart from the unique set of intervals, the algorythm would give a different path on the way up from the way down, and would force you to go up instead of down at some points, or down instead of up.