| isma | IIS Smooth Streaming Audio |
| it | Impulse Tracker Music Module |
| iti | Impulse Tracker Instrument |
| its | Impulse Tracker Music Sample |
| itz | Impulse Tracker Music Module |
| j6s | Ricoh Digital Camera Sound |
| jat | JUCE Audio Thumbnail Data |
| jcb | JCB-JCBrooke Music Module |
| jge | Roland Juno-G JGE Data |
| jgl | Roland Juno-G JGL Library |
| jo | JO Audio File |
| joy | Trackjoy GUS Tracker Song |
| jwf | Buzz Jacinth Waveform Audio |
| jwl | Buzz Jacinth Waveform Library |
| k25 | Kurzweil K2500 Data |
| k26 | Kurzweil K2600 Data |
| ka1 | Kawai K5000 Patch |
| kaa | Kawai K5000 Patch |
| kar | MIDI Karaoke Song |
| kat | Katorzer Music Composition |
| kfn | KaraFun Karaoke File |
| ki | Klystrack Instrument |
| kit | NI Battery Drum Kit |
| kmp | Korg Trinity Keymap |
| kmp3 | TKaraoke Karaoke MP3 Audio |
| korg | Korg Trinity Sample |
| koz | Audiokoz Music |
| kraw | BRSTM Audio Stream |
| kris | Kris Tracker Format Song |
| krz | Kurzweil K2000 Data |
| ksc | Korg Trinity Script |
| ksd | NI Kore Sound |
| ksds | NI Absynth Kore Patch Format Sound |
| ksf | Korg Trinity Sample |
| ksm | Ken Silverman Music |