Musicians and teachers refer to these in-between notes as "quarter-tones" ("half-flat" or "half-sharp") for ease of nomenclature, but perform and teach the exact values of intonation in each jins or maqam by ear. It should also be added, in reference to Touma's comment above, that these "quarter-tones" are not used everywhere in the maqamat: in practice, Arabic music does not modulate to 12 different tonic areas like the Well-Tempered Klavier, and so the most commonly used "quarter tones" are on E (between E-flat and E-natural), A, B, D, F (between F-natural and F-sharp) and C.