All triangles are monotone (they only have one pitch). It depends on the size of the triangle (whether it is larger and lower pitch, or smaller and higher pitch)
Clarinets play in treble clef.
the oboe reads on the treble clef and in the key of C
Treble clef.
Treble Clef
Treble clef.
Treble clef.
Treble Clef
The standard Treble clef.
Violin music is written using the treble clef.
Bass and treble clef.
treble
Saxophones usually play in the Treble Clef.