Flutes have only 2 octaves plus 2 notes

Normal Indian flutes can play only 27 notes, by whatever name we call them. This implies 12 notes with less wind and low sound, 12 notes with harder breath and higher sound. Plus additional three notes.

Present South Indian Carnatic (classical) have 8 holes. Closing first two holes is taken as sa (or c).
Tonal hierarchial rungs start from mandra madhyam ma (or f_) and two octaves end with tAra ga (or e'). Upto this 24 notes.
Additional three notes we can get with harder breath: tAr madhyam (f'), pratimadhyam (f#'), and tAr pancam pa (g').

Even if we 6 hole flutes for SI Carnatic Music, we get the same result, with minor difference in depth.

Present North Indian Carnatic (classical) have 6 holes. Closing first three holes is taken as sa (or c).
Tonal hierarchial rungs start from mandra pancam (or g_) and two octaves end with tAra tIvr madhyam (or f#'). Upto this 24 notes.
Additional three notes we can get with harder breath: tAr pancam (g'), tAr kOmal dhaivat (g#), and tAr suddh dhaivat dha (a').

OBSERVATION
With the present system of trying to produce 3 octaves from flutes which we can actually produce only two octaves, beginners may get confused.

We cannot go lower than f_ in SI and g_ in NI. We cannot go higher than g' or a'.

We can have only two breaths - light breath for 12 notes, harder breath for 12 notes. We cannot have three breaths light, medium and hard. In the traditional method, hard breath starts at ma/pa (f or g).

Instead of hypnotising ourselves that we shall get three octaves, [(two incomplete - bass and treble and one complete (middle)], we can as well go for a realistic two octave + 3 notes system.

It works like this:
Light breath. Closing all the six holes. We start with mandr shadj or c.

Hard breath: Opening the first hole, closing the remaining five holes: We start with madhya shadj or c'.

Continuation of the hard breath (slightly harder): Opening the first hole, closing the remaining six holes: We have additional c'', c#'', d''.

In other words this is a sort of Karnatic madhyam sriti or Hindusthani pancam sriti of the traditional system.


We can use this method of taking 'All six holes closed sa or c' both for the South Indian and North Indian Systems.

Advantages
Reduces confusion for beginners. Notations become easy, as Caps can be used for the middle octave and lower case small letters can be used for lower octave.

Disadvantages
Playing the traditional compositions become difficult as we cannot make use of all the three artificial octaves.

My experience with the sitar;
The main playing string (bAj tAr) starts with mandr suddh madhyam without pressing any fret(parda), (f#_) at the left end and ends with tAr madhyam (f') at the right end (bottom or kaddu). By pulling and stretching the string at f' (meenD) expert musicians produce pa' dha' ni' sa''. But this does not take place frequently. ga_ ri_ sa_ of the lower octaves are, played on the second string.


We can probably take the ma_ (f_) as sa and redesign the frets and reorganise the tones.

These suggestions, I am making not because of any arrogance or audacity, but with a humble view to reduce the difficulties of beginners of learners of classical music.

Anyway it will be for the experts and researchers to think of. I am not an expert on sitar.