| M20–M39 | Piano alone: |
| M20 | Collections, mixed (original works and arrangements; two or more composers) |
| M21 | Collections: original works, two or more composers |
| M22 | Collections: original works, one composer |
| M23 | Sonatas |
| M24 | Suites |
| M25 | Pieces |
| M26 | Piano, one hand: left |
| M26.2 | Piano, one hand: right |
| M27 | Variations |
| M28 | Marches |
| M30 | Dances—general |
| M31 | Dances—duple meter (polka, etc.) |
| M32 | Dances—triple meter (waltz, etc.) |
| M32.8 | Arrangements: collections |
| M33 | Arrangements: complete works for opera, oratorios, and cantatas (NOT piano-vocal scores) |
| M33.5 | Arrangements: excerpts from opera, oratorio, and cantatas |
| M34 | Arrangements: transcriptions (for concert purpose) of operas, oratorios, cantatas, and excerpts |
| M35 | Arrangements: orchestral and band music |
| M37 | Arrangements: concertos (NOT piano reductions of concertos for solo instrument[s] and orchestra) |
| M37.5 | Arrangements: concertos, excerpts |
| M38 | Arrangements: chamber music, part songs, music for other solo instruments |
| M39 | Arrangements: potpourris, medleys |
| M39.6 | Arrangements: piano, one hand |
| M198–M216 | Duets (piano only) |
| M198 | Three hands |
| M200 | Four hands: mixed collections (original works and arrangements) |
| M201 | Four hands: original works, collections |
| M20 | Four hands: Sonatas |
| M203 | Four hands: Suites, Variations |
| M204 | Four hands: Pieces |
| M207 | Arrangements: collections by two or more composers |
| M208 | Arrangements: operas, ballets, oratorios, cantatas (complete) |
| M208.5 | Arrangements: operas, ballets, oratorios, cantatas (excerpts) |
| M209 | Arrangements: orchestral and band music |
| M210 | Arrangements: concertos (NOT two-piano versions of concertos for solo instrument[s] and orchestra) |
| M211 | Arrangements: chamber music, songs, and part songs |
| M213 | Piano, five or more hands |
| M214 | Two pianos, two performers: original works |
| M215 | Two pianos, two performers: arrangements |
| M216 | Two or more pianos, three or more performers |
| M217–M285 | Duets (piano and other solo instruments) |
| M217–M239 | Piano and one stringed instrument |
| M240–M271 | Piano and one wind instrument |
| M272–M283 | Piano and one plucked instrument |
| M284–M285 | Piano and other (includes percussion and electronics) |
| M310–M344 | Trios (Piano and two other instruments) |
| M310–M314 | Piano and two stringed instruments |
| M315–M319 | Piano and two wind instruments |
| M320–M324 | Piano, one stringed, and one wind instrument |
| M325–M329 | Piano and two plucked instruments |
| M330–M334 | Piano, one string, and one plucked instrument |
| M335–M339 | Piano, one wind, and one plucked instrument |
| M340–M344 | Piano and other combinations |
Concertos and similar pieces
| M1010 | Piano with orchestra, full scores |
| M1010.5 | Cadenzas for such works |
| M1011 | Piano with orchestra (two-piano versions) |
| M1110 | Piano with string orchestra, full scores |
| M1110.5 | Cadenzas for such works |
| M1111 | Piano with string orchestra (two-piano versions) |
Studies and methods
| MT220 | General works |
| MT221 | Physiology of the hand (including hand exercises) |
| MT222 | Systems and methods |
| MT224 | Rudiments of music when combined with piano instruction |
| MT225–M239 | Studies and exercises |
| MT225 | General works |
| MT226 | Left hand |
| MT227 | Pedal |
| MT228 | Touch |
| MT229 | Wrist |
| MT230 | Thirds, sixths, etc. |
| MT231 | Scales and arpeggios |
| MT232 | Fingering |
| MT233 | Rhythm |
| MT235 | Phrasing |
| MT236 | Sight reading, transposition, accompaniment, etc. |
| MT238 | Polyphonic playing |
| MT239 | Performance of popular music |
| MT240 | Other |
| MT242 | Four-hand, two-piano, etc. playing |
| MT243 | Teaching pieces |
| MT245 | Instructive editions, two or more composers |
| MT247 | Instructive editions, one composer |
| MT248 | Self-instructors |
| MT250–M258 | Special pianos, including early instruments |
Classification Numbers for Books about the Piano
| ML128 .P3 | Piano bibliographies |
| ML650 | General works |
| ML651–697 | Construction: general works; by time period; by region or country; special makes; parts of the piano |
| ML700–747 | Music and playing: general works; by time period; by region or country; forms and types of music |
| MT220–255 | Piano pedagogy |
