Desired Melodies Become Mystical Puzzles!

Im actually running into the same issue. Im bringing in several genre specific melodies and riffs and I find myself having a hard time implying the same intervals and/or shapes during the figure recognition. Im spending hours trying to optimize one melody for reuse. 

I hope there is a better way...

This is a very common situation. Glad you ask. This might point to a much needed tutorial.

How can I get Synfire to consider specific melodic intervals that I want?

First off, your example figure uses 1+ which is 3 semitones at best. You need to use 0+ if you want to strongly suggest a minor second to the renderer. That is, same diatonic value plus 1 chromatic alteration. That will render the smallest possible interval.

In general, if you are trying to preserve intervals exactly, even if you manage to faithfully reconstruct them in the original phrase (what you seem to be trying), they will break as soon as you reuse the phrase in a different progression. Exact intervals are not portable. 

All you can do is suggest the smallest possible interval (as explained above) and use weak settings for VL (or disable it). If you force chromatic intervals for a segment, they will clash with the other instruments.

The vertical scale makes sure instruments don't clash. If you hear a minor second interval, it is present in the vertical scale or chord. If it's not in the chord, it MUST be in the vertical scale and Interpretation's VL needs to be relaxed such that it doesn't force a chord tone or stronger scale tone at that point.

I find it a big obstacle that certain musical ideas seemingly can’t be realized.

They can. The key is: If the intervals are not in the scale, then your melody implies a harmony change. Temporary chord changes (e.g. secondary dominants) can be very short, like 1/4 or 1/8. You don't notice them much with melodic content, except for subtle "out-of-scale" intervals and passing tones (which is what you probably have in mind).

The preview progression "Angel Eyes" is an example. Use it with melodic content and you will experience chromatic intervals that are seemingly added to the Dm chord. These are however real chord changes for only 1/4.

BTW, vertical symbols may be a better choice in your case, because they are relative to the chord. It should probably also not be based at root, but at an interval that is more likely to be next to a minor second (e.g. the 7th in a Maj7 chord).
 

I find myself having a hard time implying the same intervals and/or shapes during the figure recognition.

Trying different figure recognition settings can be tricky. Most often harmony is the culprit. It has huge influence on the resulting intervals. Unfortunately it's hard to harmonize a take with only few notes. There are just too many equally valid possibilites.

As said, faithfully reconstructing intervals in the original phrase is mostly futile. They will be at the mercy of whatever harmony you will throw at it later. Don't spend too much time on it. 

If your phrases are 4m or shorter, it's much easier to edit the result (like notating very small intervals as explained above) than to fiddle with recognition settings. I am simply nudging symbols up/down or regroup segments such that they represent what I think is the essence of the phrase.

Develop an awareness of "invisible" chord changes that are at play when you hear a certain melody. When you use progressions similar to that later on, the phrase will be preserved best.

Is using a diatonic scale versus a chromatic scale a difference ? , as a thought

Still, the major third was rendered.

Should be the horizontal symbol type and VL settings.  H-Symbols map to the horizontal scale, which is the reference scale of the key. Try using V-Symbols and weak VL settings.

Is using a diatonic scale versus a chromatic scale a difference ?

Yes, of course. Chromatic (vertical) scale allows more tension and dissonance across the board. With disabled VL you get full 12-Tone range and all the possible clashes between instruments.

With enabled VL it makes sense. VL protects at least some harmony based on the strategy you select. 

How do you assign chords to a layer? Typed input, drag & drop, pick a sub-chord?