ok your question is both simple and very deep.
Simply: similarity is in the ear of the beholder. It really depends what sound, in which context, you will find similar. It is always easy to find a sound and itself (or very very near) but as soon as you hit musical reality, you are hitting important questions.
for instance, take a C major piano chord. which of the 3 items below is nearer:
- a C# major piano chord
- a C minor piano chord
- a C major synth pad
- a tom sound
- a single C note
depending how you analyse the sound, in time, you will get a different answer. More importantly, depending when you use it, all of the above can be right. Now imagine comparing a pichy tom around C vs a single string C… how would you compare them? So deciding what to use to ‘describe’ the sound is what will change how near and far are things. Then, the range of them is important, as you read in @tedmoore’s why scale article.
The deep answer: we listen to sounds in time. So a snare shot, and a snare shot in a reverb, will have different numbers if we are not careful about how we think about time. @jamesbradbury wrote an article on dealing with time which I am yet to finish with the custom idea @weefuzzy is referring to. The code in question, if you want to check it, was in an early release so I can find it back, but I am trying to write an article around it. The ideas is to make 3 stats per slice per descriptor, as sort of envelope. for instance, you could bundle the centroid of the first 50ms, then the next 150ms, then the next 300ms of your slice, and create 3 dimensions that way.
then, you can take that concept further: you can make custom descriptors according to how you care about your material in time. For instance, @balintlaczko and I had such a discussion, and he came up with a set of descriptors that best fitted how he listened to his material in a given corpus. The thread is really informative here
If you don’t mind, let’s continue this thread, it will help me help you and others. Let me know what is not clear, and how I can clarify things more.