Alga is a notation in a musical score which is short for “all go ah.” When an orchestra reaches that point in the score, all members of the orchestra are supposed to chant “ah” simultaneously.
The timing of this can be difficult for wind instrument players. They often are required to play a note on their instrument immediately before chanting “ah.” They then have to quickly pull their instrument far enough away from their mouth such that it will not block the sound of the “ah” emanating from their mouth.
This can be a particularly difficult manoeuvre for tuba-players. Audiences have been known to interrupt performances to give a standing ovation to ovation to tuba players who pull it off with considerable dexterity and flourish.
All “ah”s are sung in C, but not always in the same octave. The octave in which orchestra members chant “ah” is indicated by the placement of “alga”on the musical staff. If it is written below the bottom of the five lines of the musical staff it is to be chanted in C2. An alga placed between the lower two lines on the staff is to be chanted in C3 and so on until an alga placed above the staff, which is to be chanted in C7.
The word alga is singular. A musical score with more than one alga is said to contain algae.