What Makes a Good Recording? Page 3
One of the more recondite aspects of recorded sound, this has no relevance whatsoever to the person unfamiliar with the sound of live acoustical instruments. To one who is familiar therewith, inaccuracies of timbre will be heard as changes in the apparent size of the instruments, which may make an English horn sound like an upper register bassoon or a brass instrument sound as though its bell is too large or too small—turning a trombone into a bass trombone or vice versa. The effect has also been compared with that of running a disc slightly off-speed but without the usual change in actual pitch: Sounds are lightened or made darker.
Freedom from distortion is easy to achieve at moderate volume levels, but clean fortissimos are another matter. Professional recording engineers developed the habit of pushing their tapes to the level limit in the days when tape hiss was the penalty for lower recording levels. With modern noise-reduction systems, recording "into the red" is no longer necessary, but is nonetheless still a common malpractice. From a tape, marginal overload is audible as a dulling of transients and, when severe, a definite sense of strain and, sometimes, audible intermodulation of highs by heavy bass information. On discs, slight tape overload can produce mistracking at levels well below where mistracking should occur with a given phono unit. On the other hand, some discs are simply over-cut, and have groove modulations so closely approaching vertical wavefronts that the stylus has no choice but to climb over them instead of following them. But if a disc will track cleanly on any cartridge, it cannot be considered overcut except on the basis of commercial practicality.
Some two-miked recordings of huge performing groups have remarkable inner detail, as though instrumental (and choral) voices were in perfect focus, while others have a diffuse or translucent quality wherein details are muddied and individual voices blurred. Blurring is usually a matter of not having found the right microphone locations; more experimentation will usually cause things to fall into sharp focus. Some halls have many "right" placements for mikes, most have a few (which are thus harder to find), while a few halls seem to have none.
Detail is also profoundly affected by the quality of the recording microphones. The lightest diaphragms (externally-polarized capacitor mikes) generally have the quickest transient response and, thus, the greatest detail.
No one is sure what makes some recordings sound liquidly transparent and others astringently dry, but it is a quality that makes some of them musically natural and others "mechanical" sounding. A transparent-sounding tape can give a transparent-sounding test cut and end up sounding dry on the final pressings.