Hi I'm new to pd, I was wondering how could I create a patch to randomly generate a melody from say, a Major scale?

@alice1 Hi, here is a patch that might help you getting started. You can look into the objects [table] (or [array define]) and [tabread] (or [array get]) to store and retrive (aka: quantise) a stream of numbers to the pitch classes of a specific scale. I think this is the simplest way to do it and allows you to quickly switch scale by sending a new set of pitches to the table.

number.to.scale.pd

As for the triggering mechanism, that is quite another story, and to algorithmically generate a melody that makes sense and is anything other than random pitches, this is a quest I'm not able to help you with (yet!).