"Now let us begin by fixing the B so that it is perfectly in tune with the E, then _without at all changing_ the B, take the interval D-B. You will see that the sixth will not be in tune. Repeat the experiment, inverting the notes: the result will still be the same. Try it yourself some time," added Mr. Betti with a smile, "and you will see. What is the reason? It is because the middle B has not been adjusted, tempered! Give the same notes to the first and second violins and the viola and you will have the same result. Then, when the 'cello is added, the problem is still more complicated, owing to the difference in _timbre_ and register. Yet it is a problem which can be solved, and is solved in practically everything we play.
"Another difficulty, especially in the case of some of the _very daring_ chords encountered in modern compositions, is the matter of balance between the individual notes. There are chords which only _sound well_ if certain notes are thrown into relief; and others only if played very softly (almost as though they were overtones). To overcome such difficulties means a great deal of work, real musical instinct and, above all, great familiarity with the composer's harmonic processes. Yet with time and patience the true balance of tone can be obtained.
"All four individual players must be able to _feel_ the tempo they are playing in the same way. I believe it was Mahler who once gave out a beat very distinctly--one, two, three--told his orchestra players to count the beat silently for twenty measures and then stop. As each _felt_ the beat differently from the other, every one of them stopped at a different time. So _tempo_, just like intonation, must be 'tempered' by the four quartet players in order to secure perfect rhythmic inflection.
"Modern composers have wonderfully improved dynamic expression. Every little shade of meaning they make clear with great distinctness. The older composers, and occasionally a modern like Emanuel Moor, do not use expression marks. Moor says, 'If the performers really have something to put into my work the signs are not needed.' Yet this has its disadvantages. I once had an entirely unmarked Sonata by Sammartini. As most first movements in the sonatas of that composer are _allegros_ I tried the beginning several times as an _allegro_, but it sounded radically wrong. Then, at last, it occurred to me to try it as a _largo_ and, behold, it was beautiful!