A Dictionary of Music and Musicians/Primo
PRIMO, 'first,' is used in two ways in music, (1) In pianoforte duets, Primo or 1mo is generally put over the right-hand page, and then means the part taken by the 'treble' player, while Secondo or 2do is put over that for the 'bass.' (2) In the reprise of the first section of a movement, a few bars are often necessary before the double-bar to lead back to the repetition, which are not required the second time of playing the section. The words Primo, 1mo, 1ma volta, or 1st time are then put over all these bars, so that when the repeated portion reaches this direction, the player goes on to the part after the double-bar, leaving out the bars over which 'Primo' is written. The first few bars after the double-bar are frequently, but not always, labelled Secondo, 2do, or 2nd time. The 'Primo' varies greatly in length. Beethoven often does without it at all (C minor and Pastoral Symphonies); in his No. 2 Symphony it is 2 bars Long, in his No. 4 it is 14 bars long, and in Mendelssohn's Italian Symphony 23 bars (1st movement in all cases).
[ J. A. F. M. ]