Stems

Every track you load gets stems: openDJ separates it with Spleeter as it loads, starting with the part around the cue point, so the stems pads work within a second or two. Nothing needs installing. The first time, openDJ downloads the stems model (about 80 MB).

The stems play over the original track: with every stem on you hear the track exactly as it is, and turning a stem down only takes that stem out. Where a part of the track isn't separated yet, the original plays.

Stems pads

Open the STEMS pad page (right-click a pad tab to put it there). The pads are laid out as in VirtualDJ:

• Vocal, Instru, Bass, Kick and HiHat mute and unmute their stem. A pad is lit while its stem plays.
• Acapella plays the vocals alone; press it again for every stem.
• Instrumental plays everything but the vocals; press it again for every stem.
• Stems FX switches the pads to echo out (the pad is lit while it's on). See below.

Set how loud each stem is with the mixer's knobs in stems mode (the EQ menu above the mixer).

On the DDJ-FLX4, press KEYBOARD twice for the stems pads, in the same layout. SHIFT + a stem's pad plays that stem alone. On the Xone K2 and the FLX4, the EQ knobs turn the stems while the mixer is in stems mode.

Echo out a stem

Press Stems FX and the stem pads echo out instead of cutting:

• A stem's pad sends that stem into an echo and mutes it, so its echo rings on and fades while the rest plays dry. Press it again to bring the stem back (any echo still ringing fades out by itself).
• Instrumental echoes out the vocals; Acapella echoes out everything but the vocals. Press again to bring them back.
• The echo is half a beat, at the track's tempo. Right-click Stems FX to pick Reverb instead.
• The stem keeps playing for half a beat after the press, so the echo has something to repeat.

The pads' corners show the effect, lit on the stems that are in it. Press Stems FX again for the normal pads. On the DDJ-FLX4, Stems FX is pad 7 of the stems pads, as on screen.

Controllers can also use Mixxx's [QuickEffectRack1_[ChannelN_StemM]],enabled to send a stem into the echo, [ChannelN],stem_fx (1 Echo, 2 Reverb) and [ChannelN],stem_fx_mode.

High quality stems

Spleeter is quick but lets a little of each stem bleed into the others. For a cleaner split, right-click a track in the browser, or a stems pad, and choose Prepare HQ Stems. openDJ separates it with HTDemucs in the background (on the graphics card; the first time it downloads the 84 MB model), one track at a time. When it's done the deck crossfades to the new stems in a fiftieth of a second, so nothing clicks even with a stem muted, and the track loads with them from then on.

The top-right stems pad shows which stems are playing: INSTANT for the quick ones made on load, HQ… while high quality ones are being prepared and HQ once they play.

Settings

Settings › Analysis › Stems has:

• Stems on load: turn it off to save CPU on an older computer. Tracks then only get stems you prepare with Prepare High Quality Stems (or from an NI stem file).
• High quality stems kept: high quality stems take about 4 times the space of the track. Once they pass this size (10 GB at first), the stems played longest ago are deleted to make room. Shows how many tracks have them and how much space they take.
• To delete them all, use Manage › Clear high quality stems under Settings › Collection › Storage.
• Whether each stems model is downloaded yet.

NI stem files (.stem.mp4) play their own stems.