This is a brief introduction to common musical instruments. This article is going to focus on woodwinds, brass, and strings. There will be a brief discussion of transposition for each instrument covered.
The most common woodwinds are the flute, oboe, clarinet, saxophone and bassoon. The flute, oboe, and bassoon are all C instruments. Therefore all three sound in concert pitch. This means that whatever note is written in the part for that musician is what sounds. If a flutist reads a middle C in treble clef (C4), then that is the pitch that will sound when the musician plays it. Same with the oboe and the bassoon.
The clarinet is a B-flat instrument. This means that the clarinet has to play a note one whole step above concert pitch to sound the same as the flute, oboe, and bassoon. Taking the middle C we discussed before, the clarinetist would need to play the D above it on their clarinet in order for it to sound as a middle C.
The last woodwind instrument is the saxophone. This is where things get more complicated. While the other woodwinds have a primary instrument and then the rest of the family (i.e., clarinet and bass clarinet, flute and piccolo, oboe and English horn, etc.), the saxophone family does not have one "primary" instrument in its family. There are four common saxophones — the B-flat soprano, the E-flat alto, the B-flat tenor, and the E-flat baritone.
The B-flat soprano reads the same as the B-flat clarinet. The B-flat soprano would have to play the D above that to have it sound as a C. The B-flat tenor sax would read the D the soprano played up one octave for it to sound in the same octave as middle C. The E-flat alto would play the A the major sixth above the concert pitch note for it to sound the same. The E-flat baritone would play the A the alto had just played up one octave for it to sound the same.
The brass family consists of trumpet, French horn, trombone and tuba. The trumpet is pitched in B-flat like the clarinet. This means if the trumpet wants to sound a middle C, like the clarinet, the musician would need to play the D one whole step higher. The French horn is pitched in F. For the horn to sound a middle C, it would need to play the G one fifth above the C. The trombone and tuba are both pitched in C and sound in concert pitch, so they would play the C in order to sound the C.
The string family includes violin, viola, cello and string bass. They are all based in concert pitch and identified by their range. The violin ranges from G3 to B6 while the viola ranges from C3 to E6. The cello ranges from C3 to C5. The string bass ranges from E2 to A3 and sounds one octave lower than written unlike the other string instruments.