Brass instrument
Tuning compensation

The additional tubing for each valve usually features a short tuning slide of its own for fine adjustment of the valve's tuning, except when it is too short to make this practicable. For the first and third valves this is often designed to be adjusted as the instrument is played, to account for the deficiencies in the valve system.

In most trumpets and cornets, the compensation must be provided by extending the third valve slide with the third or fourth finger, and the first valve slide with the left hand thumb (see Trigger or throw below). This is used to lower the pitch of the 1–3 and 1–2–3 valve combinations. On the trumpet and cornet, these valve combinations correspond to low D, low C ♯, low G, and low F ♯, so chromatically, to stay in tune, one must use this method.

In instruments with a fourth valve, such as tubas, euphoniums, piccolo trumpets, etc. that valve lowers the pitch by a perfect fourth; this is used to compensate for the sharpness of the valve combinations 1–3 and 1–2–3 (4 replaces 1–3, 2–4 replaces 1–2–3). All three normal valves may be used in addition to the fourth to increase the instrument's range downwards by a perfect fourth, although with increasingly severe intonation problems.

When four-valved models without any kind of compensation play in the corresponding register, the sharpness becomes so severe that players must finger the note a half-step below the one they are trying to play. This eliminates the note a half-step above their open fundamental.

Manufacturers of low brass instruments may choose one or a combination of four basic approaches to compensate for the tuning difficulties, whose respective merits are subject to debate:
startend:quotation, combination:two_responses