octaves hexachord octatonic tetrachords enharmonic tonic ragas notes swarams tetrachord notated thaat slendro accidentals sets raga triad submediant trichords solmization rQundgam sargam mediant intervallic triads subdominant Panchamam mixolydian janya tonal harmonic syllables tonality tones intonation quavers arpeggios fingerings fingering