<Ul> <Li> As noted earlier, certain instruments are designed for a certain key, as playing in that key can be physically easier or harder . Thus the choice of key can be an important one when composing for an orchestra, as one must take these elements into consideration . </Li> <Li> In the life of the professional clarinettist, for example, it is common to carry two instruments tuned a semitone apart (B ♭ and A) to cope with the needs of composers: Mozart's well - known clarinet concerto is in A major . To play it on a B ♭ instrument is difficult, and to rewrite all the orchestral parts to B ♭ major would be an enormous effort . Even so, it is not unheard of for a piece published in B ♭ to include notes a semitone (or more) below the range of the common B ♭ clarinet . The piece must then be played on a more exotic instrument, or transposed by hand (or at sight) for the slightly larger A clarinet . There are clarinets with an extended range, with a longer bore and additional keys . </Li> <Li> Besides this though, the timbre of almost any instrument is not exactly the same for all notes played on that instrument . For this reason a piece that might be in the key of C might sound or "feel" somewhat different (besides being in a different pitch) to an observer if it is transposed to the key of A . </Li> <Li> In addition, since many composers often utilized the piano while composing, the key chosen can possibly have an effect over the composing . This is because the physical fingering is different for each key, which may lend itself to choosing to play and thus eventually write certain notes or chord progressions compared to others, or this may be done on purpose to make the fingering more efficient if the final piece is intended for piano . </Li> <Li> In music that does not use equal temperament, chords played in different keys are qualitatively different . </Li> </Ul> <Li> As noted earlier, certain instruments are designed for a certain key, as playing in that key can be physically easier or harder . Thus the choice of key can be an important one when composing for an orchestra, as one must take these elements into consideration . </Li> <Li> In the life of the professional clarinettist, for example, it is common to carry two instruments tuned a semitone apart (B ♭ and A) to cope with the needs of composers: Mozart's well - known clarinet concerto is in A major . To play it on a B ♭ instrument is difficult, and to rewrite all the orchestral parts to B ♭ major would be an enormous effort . Even so, it is not unheard of for a piece published in B ♭ to include notes a semitone (or more) below the range of the common B ♭ clarinet . The piece must then be played on a more exotic instrument, or transposed by hand (or at sight) for the slightly larger A clarinet . There are clarinets with an extended range, with a longer bore and additional keys . </Li> <Li> Besides this though, the timbre of almost any instrument is not exactly the same for all notes played on that instrument . For this reason a piece that might be in the key of C might sound or "feel" somewhat different (besides being in a different pitch) to an observer if it is transposed to the key of A . </Li>

The principal of musical organization around a central pitch/key is called