If you read mi,fa,so,mi,do when you play b,c,d,b,g, this would mean movable do, when G is tonic (or f#,g,a,f#,d when D is tonic, etc).
Solfege doesn’t mean that we just use the names do,re,mi,fa,so,la,si,do instead of c,d,e,f,g,a,b,c. In this case this would mean that we just use the French or Italian names or other latin languages names for keys and scales.
Solfege means: Do is the root tone of the actual major key (and La is the root tone of the relative key.)
Because any of the 12 keys and their enharmonic equivalents can be the tonic we have about 17 key signs (7 major tonics of the white keys plus 5 sharp keys plus 5 flat keys and 17 minor tonics or 2x21 major and minor tonics if we include the E#, Fb, B#, Cb as scales!)
That’s the concept of the movable do: Any of these 17 or 21) keys and scales can be the tonic when the basic note of the scale is the root tone do.
Applying the movable doremi you don’t have to learn 17 keys and don’t need to imagine the intervals and relations of the tones. You just have to check that the triad domiso is on 3 neighbored lines or in 3 neighbored spaces between the lines.
With this insight and by the help of the rule that the last sharp is the lead tone si and the last flat is the lead tone fa singing and sight reading is quite easier
than counting the intervals and defining their exact distance, especially for all singers without perfect pitch.
This concept isn’t unprofessional at all. It is used in almost all countries where Western music is practiced. I have seen a documentary where Vladimir Ashkenazy was teaching Chinese school classes singing doremi.
But might be hard to understand by people who don’t have a sensory for relative pitch. And it is very difficult to explain the advantage of the movable doremi how it is impossible to describe the concept of colors to someone who is blind.
If I wouldn’t use solfege I’d imagine the numbers 1,2,3 or the R.N. from the functions theory, (degrees) or I’d recognize melodic motifs as modules like reading and recognizing words as elements instead of spelling the letters.
But I know there are musicians who just analyze and hear the intervals and say that the system of the movable do is hindering and disturbing when listening and analyzing by solmisation.
When I had to sing atonal music (e.g, Lieder from Anton Webern I was able to manage this task with the help of solfege as well by using the interval method.
Edit:
My comment to your question about Beethoven's Ode to Joy...
It makes sense to use all three methods: mi mi fa so and e e f g and 3 3 4 5 (the last makes especially sense as it is identical with the fingerings which can be applied for transposing in any other key. This might convince you of the advantage of the ** movable Do** - more evident than with 1000 words.
Additional
I think this is everyones problem that we are not aware in every situation which degree we play (e.g. when the music is modulating or in a piece of many sharps or flats).
In this case the doremi as movable Do can be helpful to memorize a tune, but I see now that it also can be confusing.
What you can do to practice is:
- Play all scales and mark the tonic, dominant and subdominant. Mind the leadtones.
- Practice the triads of all degrees in all keys.
- Study the circle of fifths.
- Play the tune with simple chords in C major or a minor.
- Transpose it in all other keys still singing it on doremi.
When listening to music notate some fix-points of orientation (marking the min. and sec. in a timeline (e.g. when you here a cadence, a sequence, a triad, an up-beat of a fourth, a passage of a scale, a lead tone, a suspension or the entry of a motif.) and after this you control what you have identified with the notes of the score.