When CDs were first released, there was some resistance to its sterility of sound compared to vinyl LPs. Part of the vinyl sound was low-level friction from the stylus in the groove, as well as the effects of equalization needed for LPs to track properly. Similarly, tape hiss and analog electronics lend a quality described as warmth that is coveted by its fans. Though many plug-ins have tried, nothing imparts the same quality to digital audio.
Perhaps the most-used feature of magnetic tape, and the most frequently simulated digitally, is its tendency to saturate in a non-linear, ear-pleasing manner. Pushing a signal beyond 0 decibels is simply not done in the digital realm. However, tape exhibits a roll-off of high frequencies and a compression effect that is frequently used to give rock drums their distinctive sound. Contemporary commercial studios often mix drums recorded digitally to magnetic tape at high levels, then load the result back into digital form.
One of the problems of the analog tape system is the requirement for it to move at a consistent and repeatable speed. Mechanical systems, even finely adjusted, still fluctuate and the effect on audio recorded to tape is distinct. When tracks are mixed and bounced down, recorded over, and layered again and again, the wow and flutter artifacts become part of the essence of the recording. Yet that effect, even though technically a flaw, provides part of the intangible analog warmth.
Digital recording is so inherently flexible that the process works around the recordist. Reel-to-reel tape forces certain ways of working. For example, rewinding is not instant-access and editing is destructive. The nature of working with tape changes the work flow. With a limited number of tracks, the need for sub-mixing, bouncing and overdubbing require more planning. Many argue that this imposes discipline on the creative process, rather than the see-what-sticks method that the luxuries of digital allows.