A Code of Practice in the Recording Industry

Inclusion of the CNSTR insignia on the CD you purchase ensures that the recorded sound more closely resembles the original sound of the orchestra, ensemble, solo instruments and vocal performance in all combinations.


The fundamental reason for the introduction of the CNSTR standard is to reassure the public that when they purchase a CD of classical music bearing the CNSTR insignia, it will have been manufactured to conform to a strict code of practice.

Previously, there have been no agreed principles in the industry: CD production companies use their individual conceptions as to what constitutes good sound, and the public is not provided with sufficient information regarding the process involved. In many cases, the sound of the CD bears little resemblance to the original, natural sound.

Geoffrey Terry’s Recollection

Listen to Geoffrey Terry recall how he first put his CNSTR theories to the test in the Royal Festival Hall, London:

Category: Sound Recording
Sub-category: Sound Recording Technique
Industry Standard

CNSTR, the acronym for Certified Natural Sound Technique Recording, is a newly-introduced standard (September 2008) for the commercial recording industry, directed in particular at manufacturers of classical music CDs. It is a voluntary code of practice for CD publishers. However, the addition of the CNSTR logo to published CDs provides assurance for the purchaser that the recording was undertaken to conform to a minimum standard. There has been an ever-growing general consensus of opinion that recordings of classical music are being over-engineered, resulting in a sound quality that is not entirely relevant to the original.

A Red Book International Standard Recording Code (ISRC) already exists. A simple example (taken from Wikipedia) can serve to illustrate:

The code USPR37300012 breaks down as follows:

The Red Book CD digital audio standard enables the encoding of ISRCs onto CDs; however, it provides no indication as to the technology employed in the actual recording process.

CNSTR has been expressed in layman’s terms since it is a reference intended for the public.

With the rapid advance in acoustic technology, the majority of recording studios have, in an endeavour to keep abreast of the times, introduced ever more complex equipment and procedures into the sound recording process: a trend which has resulted in an ever increasing difference between natural and recorded sound.

In the majority of recordings of symphony orchestras, a considerable number of microphones will be employed, positioned at strategic points amongst the players. The sound picked up by these microphones is fed to a control panel where an engineer constantly adjusts the levels in an endeavour to establish what he considers to be what the composer intended in the score.

The engineer is undertaking to correct the directions of the conductor who, from a musical point of view, is better qualified to perform the task.

With CNSTR, only two microphones are utilised. The task of the recording engineer is to establish the best positions for the microphones so that they faithfully capture the full spectrum of the orchestra and simulate a left and right image that would be heard if sitting in an optimum position in the audience.

Prior to the recording, the engineer should establish the maximum level of sound likely to be produced by the ensemble, with the level controls being set to that position and no further corrections or alterations being made during the performance.

Following completion of the recording process, any extraneous noises, tape hiss or coughing should be removed. There the process terminates, the resultant recording being a natural sound by virtue of the fact that it has not been transformed in any way electronically. Multiple reproductions (CDs) of the recording can then be produced without any additional electronic processing.

CD producers who voluntarily adhere to the criteria are permitted to add the CNSTR insignia to their CDs.

CNSTR Samples

Here are a few samples of CNSTR recordings (see the Samples page for a full index of all the sound samples on this site):

Frederick Delius: Irmelin PreludeCD1/2008
Recorded in the Royal Festival Hall, London, 1966
Giuseppe Verdi: La Forza del Destino: Act I(N/A)
Recorded in the Victoria Theatre, Newcastle upon Tyne, 1966
Royal Festival Hall Organ
(Recorded during a rehearsal with no audience present)
Recorded in the Royal Festival Hall, London, 1967

As with the other sound samples on this site, please note that in order to keep the files down to a manageable size, the quality of the MP3s has been greatly reduced. As such, the quality of these samples is not representative of the quality of the CD-based recordings.