I'm sure you don't really need to know, but the difference between EM and P4 is as follies:


All these standards apply to 4mm to the foot, or 1/76.4.

EM gauge is to 18mm gauge (scale 4'6" as against actual 4'8.5")) with BRMSB finescale wheel standards. These have thicker, deeper flanges and wider treads than true scale, but rather closer to scale than OO standards, and certainly very much closer than OO scale was in 1950 or so when the British Railway Model Standards Bureau (a trade association) set the standard.

P4 is very close to exact scale reproduction of track and wheel dimensions, with only very minor deviations to accommodate the limits of economic manufacturing tolerances and the much sharper than scale curves generally found on models. Gauge is 18.83mm, scale 4'8.64", or scale 140 thou overgauge.

OO runs to a scale gauge of 4'1.5"!

The difference is best seen in of the track:

OO
EM
P4

How can it apply to music? Well, the P4 man is very concerned with certain aspects of authenticity, especially as regards dimensions. As there is very little available off- the- shelf, he spends a lot of time ensuring things are right. The trains run slowly at scale speeds, usually with fully authentic signalling and procedures. The scene is often quite sparse, because there is little room for scale curves in most people's houses.

The OO man is more concerned with easily getting things going and enjoying his models. The trains often run round much sharper curves so as to cram more uintricate track in, and it often runs faster.

The EM man is somewhere inbetween, and these days usually represents a purist of an earlier period.

I enjoy all types, and here endeth the parable.