from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Music A series of four diatonic tones encompassing the interval of a perfect fourth.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. In music a tetrachord is any set of four different pitch classes.
from the GNU version of the Collaborative International Dictionary of English
- n. A scale series of four sounds, of which the extremes, or first and last, constituted a fourth. These extremes were immutable; the two middle sounds were changeable.
from The Century Dictionary and Cyclopedia
- n. In music: An instrument with four strings.
- n. The interval of a perfect fourth.
- n. A diatonic series of four tones, the first and last of which are separated by a perfect fourth.
Greek tetrakhordon, from neuter of tetrakhordos, four-stringed : tetra-, tetra- + khordē, string; see gherə- in Indo-European roots.(American Heritage® Dictionary of the English Language, Fourth Edition)