| I | (Italian) the (masculine plural) |
| Idyll | a musical composition of peaceful pastoral character |
| Il | (Italian) the (masculine singular) |
| Il faut | (French) there is needed, there are needed |
| Im Bedarfsfalle | (German) in case of need |
| Im Falle | (German) in case |
| Immer | (German) ever, always, still |
| Impair | (French) odd (numbers) |
| Impaziente, Impazientemente | (Italian) impatient, impatiently |
| Imperioso | (Italian) imperious |
| Impeto | (Italian) impetus, impetuosity |
| Impétueux (Fr.), Impetuoso (It.), Impetuosamente (It.), Impetuosità (It.) | impetuous, impetuously, impetuosity |
| Imponente (It.), Imponierend (Ger.) | imposing in style |
| Imponenza | (Italian) an imposing style |
| Impromptu | an instrumental piece giving the impression of having been improvised |
| Incalcando | (Italian) getting louder and faster |
| Incalzando | (Italian) hastening, pressing forward |
| Inciso | (Italian) incisive |
| Incominciando | (Italian) commencing |
| Indebolendo | (Italian) becoming weaker |
| Indeciso | (Italian) undecided, capricious |
| Indicato | (Italian) prominent |
| Infra | (Italian) below |
| Inglese | (Italian) English |
| In modo di | (Italian) in the manner of |
| Innig | (German) heartfelt |
| Inno | (Italian) Hymn |
| Innocenza | (Italian) innocence |
| In nomine | an instrumental fancy based on the plainsong (Gloria Tibi Trinitas Aequalis) |
| Inquiet (Fr.), Inquieto (It.) | restless |
| Insensible | imperceptible |
| Insieme | (Italian) together, ensemble |
| Inständig | (German) urgent |
| Instante | (Italian) urgent |
| Intavolatura | a term used in Elizabethan times for the arrangement of madrigals |
| Intermède (Fr.), Intermezzo (It.) | a smaller piece placed between others, a small independent piece |
| Intime (Fr.), Intimo (It.) | intimate |
| Intoning | chanting on a single note |
| Intrada | (Italian) entrée |
| Intrepido, Intrepidezza | (Italian) bold, boldness |
| Introduzione | (Italian) introduction |
| Ironico, Ironicamente | (Italian) ironic, ironically |
| Irresulto | (Italian) indecided in style |
| Islancio | (Italian) impetuosity |
| Isometric | where the rhythm in each part exactly matches that in the other(s) so the structure is chordal rather than contrapuntal |
| Isorhythmic | repeated rhythmic pattern although with a change of notes |
| Istesso | (Italian) same |
| Istrumento d;acciaio | glockenspiel |
| Italian Sixth | a form of augmented sixth (in the key of C: the notes 'A flat, C, F sharp') |