Natural horn is the valve-less

predecessor of the modern horn. Valve-less brass instruments are

restricted

to the notes of the overtone series by the laws of acoustics. This meant

that

the only way to play melodic passages was to play in the extreme upper

register. Eventually, horn players

devised methods to overcome this obstacle and play melodically in what

we have come to think of as their most characteristic range. They

achieved this by inserting their right hands into the

bell and shading the open notes. This technique relied upon the players

ability to match the tone quality

of the closed and open notes as much as possible, and is the reason we

still use

our right hands in the bell of the modern horn to control both tone

quality and

pitch. This technique worked

well for tonal music, with the horn pitched in the key of the piece

(i.e.

Concerto in D is written for horn in D), but it had severe

limitations in

more chromatic music. It was really only practical to make the sound of

the

closed and open notes match up enough in a very limited (and soft)

dynamic

range. To change keys a system of removable

crooks was developed. A crook is a lead-pipe with enough tubing to make

the horn play in a certain key. Later developments moved the crooks to

the tuning slide  so that the lead-pipe could remain fixed in place

(inventionshorn).
Berkeley have this horn are come with total 6 set

of tuning pipe. that is most tuning slide you can get. and you can play

in any key you like