What is "bass oboe"

The bass oboe or baritone oboe is a double reed instrument in the woodwind family. It is about twice the size of a regular (soprano) oboe and sounds an octave lower; it has a deep, full tone somewhat akin to that of its higher-pitched cousin, the English horn. The bass oboe is notated in the treble clef, sounding one octave lower than written. Its lowest note is B (in scientific pitch notation), one octave and a semitone below middle C, although an extension may be inserted between the lower joint and bell of the instrument in order to produce a low B. The instrument's bocal or crook first curves away from and then toward the player (unlike the bocal/crook of the English horn and oboe d'amore), looking rather like a flattened metal question mark; another crook design resembles the shape of a bass clarinet neckpiece. The bass oboe uses its own double reed, similar to but larger than that of the English horn.