Note that the above standard revolver (roll-changer) invented by Leopold King does not have a friction speed control, nor any other self-contained mechanical provision to adjust the tempo of the music roll. For machines destined for the European market it was common to adjust the tempo by using an electrical resistance that changed the motor speed, which also, of course, slowed or speeded up the feeder bellows (pumps) too.

For the American market, a cone drive (consisting of two tapered cones, one inverted, connected by a small flat belt) was used in early PianOrchestras. This was quickly supplanted by a very durable and trouble free friction-disk speed control, which became a standard fixture on all Philipps revolvers in instruments imported by Wurlitzer.

The catalogue description of the revolver-mechanik (taken from the English portion) is shown verbatim (sic) below. Although the Philipps catalogue is fundamentally German, there are English and French insets for most subjects, thereby accommodating the English and French speaking markets.

By means of this patent unrivalled invention 6 Music Rolls can be inserted in our instruments at a time and change automatically, differing only from ordinary ones in that they have a piece of linen attached to the beginning of the paper enclosed in a brass sheath. If 6 of such rolls are inserted, then without the assistance of a third person, the Rolls succeed each other automatically, unrolling and placing themselves in position until all are finished, when they can be removed in the simplest manner either altogether or singly.

A further advantage is that there is less risk of derangement by unskillful handling and the rolls are kept in better condition, not being so frequently changed.

It is easy to see the advantage which the automatic system has over the other, and to the busy Hotel-Manager it is a special boon, enabling him to provide for his guests a highly varied programme of Concert and Dance Music without trouble of any sort.

Besides this, each Roll can if desired consist of 4 or more pieces of Music, so that with a single insertion of 6 rolls a programme of 24 or more pieces is obtained.

This invention can be used by no other makers and for that reason we claim the first place to-day in our branch of industry.