Pneuma
Breath; also long melismas in chant.
What it means
Pneuma is the Greek word for breath or breathing. In the chant tradition the term is used for long, textless melismas, such as stand especially at the end of an Alleluia; what is meant is a song that detaches itself from the word and becomes, as it were, only breath. With the word neuma, which designates the signs of early musical notation, there is a linguistic closeness that leads to confusions in the sources; the terms are not used uniformly.
Musical use
Textless melismas in the liturgy are no ornament but have a rank of their own: they stand at elevated points and express a joy for which words were considered insufficient. They are consequential for music history, because the subsequent underlaying of texts to such melismas led to the emergence of the sequence and the trope — two genres that gained great scope in the Middle Ages. Here a procedure typical for the development of music shows itself: a new form arises from a practice of performance.
Performance practice
Organize long melismas into sections and breathe at the marked points; an unprepared breath in the middle of the line destroys the coherence. Keep the vowel the same over the whole stretch, so that the sound remains closed. Sing without vibrato and with calm tone production, and shape in groups rather than in individual notes. When practising, look for recurring turns — they ease memorization. Statements about the meaning of the term in the literature are inconsistent and should be checked against the respective source.
Bear in mind that the terms pneuma and neuma lie close together in the sources and are confused: check in each case whether a melisma or a notation sign is meant. For performance it holds to organize long melismas and to breathe at the marked points. Inform yourself about the neume signs that indicate the course of the melisma in the sources. The interpretation is not conclusively settled in scholarship.