The Trombone Slide

 

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Now weíll turn our attention to a real instrument: the trombone.Aside from the bugle, the trombone is the simplest brass instrument.Itís basically a low-pitched bugle with a variable pipe length.

 

A trombone slide has seven positions, each one representing a semitone.The positions are numbered from 1 to 7.Position1 is when the slide is fully contracted, and the pipe is the shortest.Position 7 is when the slide is fully extended, and the pipe is the longest.The lowest note played in position 1 is Bb2.Position 2ís lowest note is A2, and so on.Position 7ís lowest note is E2, and is the lowest note that a trombone can normally play.

 

So far, so good.But how do you get twelve semitones from only seven positions?The answer is that all notes that a trombone plays are harmonics of the pipe length.For example, when playing Bb2 in position one, the pipeís true fundamental is actually Bb1, one octave lower.These fundamentals range from Bb1 down to E1, and are called pedal tones.Although itís possible to play them, their sound is very weak, and little music is written for them.

 

Letís look closely at position 1.The pipeís fundamental is Bb1, but weíre not going to write music for that, because the tone stinks.So the lowest note weíre actually going to play is Bb2, the pipeís second harmonic.Remember from the bugle that brass players can play higher harmonics by controlling their embouchure.Now, whatís the third harmonic of Bb1?Itís F3, seven semitones above Bb2, the second harmonic.Seven semitones?Itís no accident that a trombone slide has seven positions:itís just enough to reach down from F3 to Bb2.

 

Letís go up a little higher.The fourth harmonic of Bb1 is Bb3.Bb3 is five semitones above F3, the third harmonic, so we need only five slide positions to reach down from Bb3 to F3.

 

It turns out that those seven positions are enough, after all.Below is a chart that displays the notes in the standard trombone range (skilled players can play higher).

 

Note

Slide Position

Pipe Fundamental

Harmonic

E2

7

E1

2

F2

6

F1

2

Gb2

5

Gb1

2

G2

4

G1

2

Ab2

3

Ab1

2

A2

2

A1

2

Bb2

1

Bb1

2

B2

7

E1

3

C3

6

F1

3

Db3

5

Gb1

3

D3

4

G1

3

Eb3

3

Ab1

3

E3

2

A1

3

F3

1

Bb1

3

Gb3

5

Gb1

4

G3

4

G1

4

Ab3

3

Ab1

4

A3

2

A1

4

Bb3

1

Bb1

4

B3

4

G1

5

C4

3

Ab1

5

Db4

2

A1

5

D4

1

Bb1

5

Eb4

3

Ab1

6

E4

2

A1

6

F4

1

Bb1

6

Gb4

5

Gb1

8

G4

4

G1

8

Ab4

3

Ab1

8

A4

2

A1

8

Bb4

1

Bb1

8

 

 

 

Some trombone Q&A

 

 

 

 

 

Finally, a patch

 

Letís use this knowledge to convert our bugle into a trombone.Below is a trombone patch.

 

 

 

 

How does it work?

 

The tromboneís audio chain is almost identical to the bugle:thereís a loop made between a lip filter and a pipe.The big difference is in the tuning of the two sections:

 

 

 

The G2 has a wide variety of logic modules, and there are various ways of converting note numbers to slide positions.This patch uses a pair of SeqCtr modules to create a 32-note range, from E2 to B4.Weíll first add 24 to the note number, so that E2 is zero.Multiplying the result by 4 makes the left-most SeqCtr increase by one stage for each note.Subtracting 16 from the note and multiplying by 4 again makes the right-most SeqCtr address the next 16 notes.Since SeqCtrs ďparkĒ their outputs to zero when the Ctr input is out of range, our SeqCtrs donít interfere with each other.

 

The outputs of the SeqCtrs adjust the pitch of the delay line, in semitones.If a note should be played in position 1, the SeqCtr output for that note is zero.If a note should be played in position 2, the SeqCtr output for that note is -1, lowering the pipeís pitch from Bb1 to A1.Position 7, E1, is achieved by setting a SeqCtr value to -6.

 

Glide modules are included to smooth the tuning of both the lip filter and the pipe.