# Brass Compensation



## Enthalpy

Hi dear friends!

I seek advice from brass players, since I only played the Bb tuba for 3 months without a professor. And this thread shall also attract more inputs about *compensating systems and techniques*.

The fourth valve makes a fourth interval. The third valve alone makes a small third interval. But *combined with the fourth, the third valve adds a full tone* more closely than a small third. So I decided to use the combination that way. *Is that the normal practice?*

Simple computations support that idea. Adding tubing length as if the bore were a cylinder open at both ends, and assuming for simplicity that all slides are tuned for perfect individual action:



Code:


0.0595 Length added by semitone slide
0.1225 Length added by full tone slide
0.1892 Length added by minor third slide
0.3348 Length added by perfect fourth slide
--------------------------------------------
0.5168 Added by perfect fourth plus tone plus semitone slides
0.4983 Needed for perfect fifth, combination is 21 cents low
0.5874 Needed for minor sixth, combination is 79 cents high
--------------------------------------------
0.5241 Added by perfect fourth plus minor third slides
0.4983 Needed for perfect fifth, combination is 29 cents low
0.5874 Needed for minor sixth, combination is 71 cents high
--------------------------------------------
0.5835 Added by perfect fourth plus minor third plus semitone slides
0.5874 Needed for minor sixth, combination is 4 cents high
0.6818 Needed for major sixth, combination is 104 cents high


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## david johnson

Sorry, I don't understand that very well. Are you asking about tuning the intervals? In general - 3rd valve alone is usually flat-sounding and 1-2-3 is usually sharp.


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## Enthalpy

Bb tubas have usually a fourth valve that gives a perfect fourth. When combined with that fourth valve, the third is closer to a full tone than a small third. So I wonder if it's normal practice to use it as a full tone then.


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## ShaunRoche

Hi there, just chanced upon this thread - is your instrument like a European/British Brass Band BBb Tuba with piston vales or like an out and out Orchestral or German Beer Keller instrument with rotary vales? If the former, then read on...

Firstly, the Bb Tuba, in Brass Band terms is probably the most difficult of all the Brass Band instruments to play in so much that it appears that the notes on the other instruments are generally a very similar space apart tonaly. This is a difficult concept to explain...what I mean is that when one plays a scale on another less large scale instrument, as one goes up or down, the notes seem effortlessly close to each other..on the Bb Tuba as you progress through the scale, the next note instead of just being there, requires more adjustment of the embouchure to such an extent that when you arrive at that that particular note when playing a melody or whatever, one has to _know _where it is on the instrument rather than it just being next to the preceding note in the scale....I'm sure this is something to do with note frequency due to the length of pipework or whatever...

Anyway, personally I wouldn't trouble yourself with the mechanics of the intervals and the fourth valve.....If your instrument has three vales for the right hand and the fourth vale for the left hand, then just try this....the fourth valve initially is a substitute for vales 1 & 3...a D for instance in treble clef would be valves 1 & 3 - you would normally play this with just the 4th valve as you would a lower G below the same stave and clef. The next note down, the F natural would be 1 & 4...F# by contrast would be 2 & 4, mimicking the 2nd valve when one plays an F# on the stave rather than below it, so you can see, the 4th valve is just adding the ability to get those lower notes without adding lots of tubes and therefore increasing the propensity for intonation issues due to all that additional tubing, not to mention all that additional breath required to fill it...

As an aside, one wouldn't tend to use just the 3rd valve by itself as this mimics 1 & 2 and would only tend to be used if 1 & 2 gave intonation problems that couldn't be solve by the change of embouchure of tube length.

Not sure if any of the above has helped, but it's made me feel better!


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