Stemz: AI Tool for Musicians

Review by eFreeware

Stemz: AI Tool for Musicians is a free Android app from MWM. The pitch is simple: bring in a song you already own, and the app pulls it apart into vocals, guitar, piano, drums and bass so you can work with the pieces rather than the finished recording.

That idea is what makes it worth a look. Instead of hunting for a backing track that may not exist, or settling for a version in the wrong key, you start from the recording you actually want to play along with. Singers, guitarists, pianists, drummers, bass players and dancers are the audiences the app targets, and it has been downloaded more than a million times with a 4.3 average from over 12,500 ratings, so a fair number of people have taken that idea seriously.

It is free to download and carries no ads, though there are in-app purchases. I would treat it as a practice and remix tool rather than a full production suite: the whole design revolves around separating a track and reshaping the resulting parts.

How the separation actually works

The centerpiece is source separation. You select the tracks you want to edit, and the app extracts and isolates the instruments it lists: vocals, guitar, piano, drums and bass. The developer calls the algorithm the most advanced available, which is the sort of claim every app in this category makes, and the sensible way to read it is as an ambition rather than a guarantee.

What matters more is what you can do once the parts exist. Each stem has a slider, so you can raise the drums and pull the vocals back, or mute a part entirely and play it yourself. The developer also mentions cutting stems instantly, which suggests you can trim a section down to the bars you need instead of working with the whole song.

There is a second layer of control in the option to pick the best group of stems for your track. Songs differ in what they contain, and choosing the right set before you start editing is a small decision that saves fiddling later.

Getting your own audio in

You bring audio in from iCloud, Drive or Dropbox through the Files apps. That covers the usual ways people store music and recordings, and it means the app works with material you already have rather than a catalog it supplies itself.

There is a second route that I find more interesting for anyone who records themselves: you can extract the audio from videos in your Camera Roll. A phone recording of a rehearsal, a lesson or a live take can become a track you separate and work on. For teachers, that opens up the possibility of pulling a student's own performance apart, which is a more personal exercise than using a commercial release.

Once a mix is finished, you can share the result with friends. Export uses M4A or CAF, both standard formats, so the files should slot into whatever else you use without conversion headaches.

What it asks of you

Stemz is free to download and shows no ads, but it does offer in-app purchases. The app is rated for Everyone, and the developer's own framing is aimed at musical beginners as much as professionals, so nothing about the presentation is meant to intimidate.

The real requirement is material. The app separates songs you bring to it, so you need audio files you can legitimately use, whether that is your own recordings or tracks you have the right to work with.

The other thing to weigh is scope. This is a separation and remix tool with a defined set of parts, not a recording studio. It gives you vocals, guitar, piano, drums and bass, and it gives you sliders and cuts to shape them. The app concentrates on working with existing recordings rather than building arrangements from scratch.

Ways to put it to work

The most obvious use is practice. A guitarist can drop the guitar part and play over what remains; a singer can lower the vocal and take the lead; a drummer can keep the click of the original performance while removing everything else. Because each part has its own slider, you can also start with the full mix and gradually remove elements as you learn a song, which is a gentler way to build up to playing along.

Dancers get something slightly different out of it. Isolating a drum or bass line gives a cleaner rhythmic reference than a full mix, and trimming to a section makes it easier to loop a passage for repetition. Music teachers can use the same mechanics to break a piece into its components for a student, pointing at one instrument at a time instead of asking someone to pick it out of the whole.

For producers and DJs, the appeal is in reworking material: pulling a vocal out of one track, keeping the drums from another, and exporting the combination as a new file. The export and share options make that workflow plausible for both groups. I would expect the results to be most convincing when the source recording is clean and the parts are reasonably distinct to begin with; dense mixes with heavily layered instruments are harder for any separation tool to unpick.

Where the limits sit

That covers a great deal of popular music, but it is a fixed set rather than an open-ended instrument list, and anything outside it will not have a dedicated stem of its own.

There is also the matter of the in-app purchases. The app is free and ad-free, which is a comfortable starting position, but the presence of purchases means the full experience may involve spending at some point.

Finally, the accuracy claim deserves a measured reading. Calling an algorithm the most advanced is marketing language, and separation quality varies with the material. Treat the first result as a starting point you can adjust with the sliders rather than a finished, studio-grade split.

A worthwhile tool for players and teachers

Stemz suits anyone who wants to play along with real recordings and is willing to bring their own audio. The combination of import from cloud storage, camera-roll audio extraction, five separable parts, per-stem sliders and export in M4A or CAF covers the practical needs of practice, teaching and remixing without demanding much setup.

It suits guitarists, bassists, pianists, drummers, singers and dancers who already have a library of tracks or recordings they can use, and teachers who want to show students how a piece is put together. Producers and DJs looking to rework material will find the same mechanics useful, provided they accept that separation is an approximation rather than a perfect extraction.

The app is free to download, carries no ads, and has been around long enough to accumulate a large user base and a solid average rating. With in-app purchases in the mix and a fixed set of instruments, it is not unlimited, but for the job it sets out to do, the package is coherent and the price of entry is low.