A prima vista
Played from sight, without prior practice.
What it means
A prima vista means “at first sight” and denotes playing or singing from the page: a notated text is performed without having practised it beforehand. In English one speaks of sight-reading or sight-singing, in French of à vue.
Sight-reading is to be distinguished from improvisation. There the music is invented in the moment; here an existing text is read and realised in the moment. It is likewise to be kept apart from playing from memory, in which the text has already been internalised.
The expression also denotes a skill that is specifically practised in musical training and that belongs to the craft of répétiteurs, orchestral musicians and accompanists.
In the notation
As an instruction the phrase appears rarely; it describes a situation, not a manner of performance. In examination and teaching literature it stands above pieces intended for practising sight-reading. Occasionally it is also found in collections whose pieces are deliberately kept easy, so that they can be managed without preparation.
Musical use
Sight-reading has always belonged to professional practice. In times when music was written predominantly for immediate use, it went without saying that musicians performed unfamiliar pieces straight away. Today too it is an everyday matter in orchestral service, in song accompaniment and in church music. In competitions and entrance examinations it forms a task of its own.
Sight-reading is a basic skill for répétiteurs, orchestral musicians and church musicians, and is tested in entrance examinations and auditions. It calls for reading ahead, recognising patterns and playing on through mistakes. Regular practice with unfamiliar material improves it more than any single exercise.
Performance practice
Before the first note, gain an overview: key, time signature, tempo, striking passages, repeat marks. Choose a tempo you can hold at the hardest passage, not at the beginning. Read ahead — the eye should always be a bar further on than the hands. And keep the pulse going even when notes are missing: playing on matters more than completeness.