| K | when followed by a number, catalogue number of Mozart's musical works, see Köchel |
| Kammer | (German) chamber, as in 'chamber music' |
| Kanon | (German) canon |
| Kapelle | (German) chapel |
| Kapellmeister | (German) the director of the chapel music |
| Kastagnetten | (German) castanets |
| Kaum | (German) barely |
| Keck, Keckheit (noun form) | (German) audacious, audacity |
| Keineswegs | (German) no way |
| Kettledrum | timpani |
| Key-note | tonic |
| Kielflügel | (German) harpsichord jack |
| Kind, Kinder, Kindlich | (German) child, children, childlike |
| Kirche | (German) church |
| Kirchencantate | (German) church cantata |
| Kissentanz | (German) cushion dance |
| Kit | a small pocket violin popular with dancing masters who could play and demonstrate the dance steps at the same time |
| Klagend, Kläglich | (German) lamenting, lamentable |
| Klar | (German) clear, distinct |
| Klarinette, Klarinetten, Kl. (abbreviation) | (German) clarinet, clarinets |
| Klaviatur, Klavier | (German) keyboard |
| Klavierauszug | (German) piano arrangement |
| Klavierstück | (German) piano piece |
| Klavierübung | (German) keyboard exercise |
| Klein, Kleine | (German) small, minor |
| Kleine Trommel | (German) side drum, snare drum |
| Kleinflüte, Kl. (abbreviation) | (German) piccolo |
| Klingen, Klingend | (German) to sound, resonant |
| Knarre | (German) rattle |
| Kneifend | (German) plucking, pizzicato |
| Kokett | (German) coquettish |
| Kolomyika | a quick duple-time Polish dance |
| Kolophone | (German) bow resin, bow rosin |
| Koloratur | (German) coloratura |
| Kombination | (German) combination, choice of organ registration |
| Komisch | (German) comic |
| Komponiert | (German) composed |
| Kontrabass | (German) double-bass |
| Kontrabassposaune | (German) double-bass or contrabass trombone |
| Kontrafagott | (German) double bassoon |
| Konzert | (German) concert, concerto |
| Koppel | (German) coupler (organ, harpichord) |
| Kornett | (German) modern cornet, early cornetto |
| Kostenka | (German) a type of Serbian dance |
| Kraft | (German) strength, vigour |
| Kräftig | strong, vigorous |
| Kreis | (German) cycle, circle |
| Kreuz | (German) the sharp sign |
| Kreig | (German) war |
| Krummbogen, Krummbügel | (German) crook of a brass instrument |
| Krummhorn, Krumhorn | (German) crumhorn |
| Kujawiak | a quick, triple-time Polish dance |
| Kunst, Künstler, Kunstkenner | (German) art, artist, connoisseur |
| Kurz, Kurze | (German) short |