Library of Congress call numbers group books by topic. Research topics in Education can be interdisciplinary, which means there may be many areas in the Library of interest. The following are some you might find useful.
MT1-960 Musical instruction and study
ML1-5 History and criticism
MT5.5-7 Music theory
MT20-32 Special methods
MT40-67 Composition. Elements and techniques of music
MT58-67 Forms
MT68 Improvisation. Accompaniment. Transposition.
MT70-74 Instrumentation and orchestration
MT73 Band
MT90-146 Analysis and appreciation of musical works
MT95-100 Opera, ballet, etc.
MT110-115 Oratorios, cantatas, etc.
MT125-130 Orchestral music
MT140-145 Chamber and solo instrumental music
MT146 Popular music
MT170-725 Instrumental techniques, Solo Instruments
MT180-198 Organ
MT192 Electronic keyboard instruments
MT200-208 Reed organ
MT220-255 Piano
MT259-338 String instruments
MT260-279.7 Violin
MT280-298 Viola
MT300-318 Violoncello
MT320-334 Double bass
MT339-533 Wind instruments
MT340-359 Flute
MT360-379 Oboe
MT380-392 Clarinet (A, Bb, C, Eb, etc.)
MT400-415 Bassoon
MT418 Brass instruments
MT420-432 Horn
MT440-456 Trumpet
MT460-472 Trombone
MT480-488 Tuba
MT500-510 Saxophone
MT539-654 Plucked instruments
MT540-557 Harp
MT560-570 Banjo
MT580-599 Guitar
MT600-612 Mandolin
MT620-634 Zither
MT640-654 Lute, balalaika, etc.
MT655-725 Percussion and other instruments
MT 728-735 - Instrumental Techniques - Ensembles
MT728-728.3 Chamber music
MT730 Orchestra
MT733-733.6 Band
MT740-810 Instrumental technique for children
MT820-915 Singing and voice technique
MT825-850 Systems and methods
MT855-883 Special techniques
MT898-915 Techniques for children
MT918-948 School music
MT955-956 Musical theater