How Meta’s AI Generates Music Based on a Reference Melody | by Max Hilsdorf | Jun, 2023


MusicGen, analyzed

Picture by writer.

On June thirteenth, 2023, Meta (previously Fb) made waves within the music and AI communities with the discharge of their generative music mannequin, MusicGen. This mannequin not solely surpasses Google’s MusicLM, which was launched earlier this yr, by way of capabilities however can also be educated on licensed music information and open-sourced for non-commercial use.

This implies that you would be able to not solely learn the research paper or take heed to demos but in addition copy their code from GitHub or experiment with the mannequin in an online app on HuggingFace.

Along with producing audio from a textual content immediate, MusicGen also can generate music primarily based on a given reference melody, a characteristic referred to as melody conditioning. On this weblog submit, I’ll reveal how Meta carried out this convenient and interesting performance into their mannequin. However earlier than we delve into that, let’s first perceive how melody conditioning works in observe.

Base Observe

The next is a brief digital music snippet that I produced for this text. It options digital drums, two dominant 808 bass and two syncopated synths. When listening to it, attempt to establish the “fundamental melody” of the monitor.

Utilizing MusicGen, I can now generate music in different genres that stick with the identical fundamental melody. All I would like for that’s my base monitor and a textual content immediate describing how the brand new piece ought to sound.

Orchestral Variant

A grand orchestral association with thunderous percussion, epic brass fanfares, and hovering strings, making a cinematic ambiance match for a heroic battle.

Reggae Variant

traditional reggae monitor with an digital guitar solo

Jazz Variant

easy jazz, with a saxophone solo, piano chords, and snare full drums

How Good are the Outcomes?

Though MusicGen doesn’t adhere intently to my textual content prompts and creates music that’s barely totally different from what I requested for, the generated items nonetheless precisely replicate the requested style and, extra importantly, each bit showcases its personal interpretation of the principle melody from the bottom monitor.

Whereas the outcomes aren’t excellent, I discover the capabilities of this mannequin to be fairly spectacular. The truth that MusicGen has been probably the most widespread fashions on HuggingFace ever since its launch additional emphasizes its significance. With that mentioned, let’s delve deeper into the technical features of how melody conditioning works.

Three text-music pairs as they’re used for coaching fashions like MusicLM or MusicGen. Picture by writer.

Nearly all present generative music fashions comply with the identical process throughout coaching. They’re supplied with a big database of music tracks accompanied by corresponding textual content descriptions. The mannequin learns the connection between phrases and sounds, in addition to methods to convert a given textual content immediate right into a coherent and pleasing piece of music. Throughout the coaching course of, the mannequin optimizes its personal compositions by evaluating them to the true music tracks within the dataset. This permits the mannequin to establish its strengths and areas that require enchancment.

The difficulty lies in the truth that as soon as a machine studying mannequin is educated for a particular job, similar to text-to-music era, it’s restricted to that exact job. Whereas it’s potential to make MusicGen carry out sure duties that it was not explicitly educated for, like persevering with a given piece of music, it can’t be anticipated to deal with each music era request. As an example, it can not merely take a melody and rework it into a special style. This might be like throwing potatoes right into a toaster and anticipating fries to return out. As a substitute, a separate mannequin should be educated to implement this performance.

Let’s discover how Meta tailored the mannequin coaching process to allow MusicGen to generate variations of a given melody primarily based on a textual content immediate. Nevertheless, there are a number of challenges related to this strategy. One of many main obstacles is the paradox in figuring out “the melody” of a track and representing it in a computationally significant manner. Nonetheless, for the aim of understanding the brand new coaching process at a broader stage, let’s assume a consensus on what constitutes “the melody” and the way it may be simply extracted and fed into the mannequin. On this state of affairs, the adjusted coaching methodology will be outlined as follows:

Three text-music-melody pairs as they have been used for instructing MusicGen melody-conditioned era.

For every monitor within the database, step one is to extract its melody. Subsequently, the mannequin is fed with each the monitor’s textual content description and its corresponding melody, prompting the mannequin to recreate the unique monitor. Primarily, this strategy simplifies the unique coaching goal, the place the mannequin was solely tasked with recreating the monitor primarily based on textual content.

To grasp why we do that, let’s ask ourselves what the AI mannequin learns on this coaching process. In essence, it learns how a melody will be changed into a full piece of music primarily based on a textual content description. Which means that after the coaching, we will present the mannequin with a melody and request it to compose a bit of music with any style, temper, or instrumentation. To the mannequin, this is identical “semi-blind” era job it has efficiently completed numerous instances throughout coaching.

Having grasped the approach employed by Meta to show the mannequin melody-conditioned music era, we nonetheless must deal with the problem of exactly defining what constitutes “the melody.”

The reality is, there isn’t a goal methodology to find out or extract “the melody” of a polyphonic musical piece, besides when all devices are taking part in in unison. Whereas there’s typically a distinguished instrument similar to a voice, guitar, or violin, it doesn’t essentially indicate that the opposite devices aren’t a part of “the melody.” Take Queen’s “Bohemian Rhapsody” for instance. If you consider the track, you would possibly first recall Freddie Mercury’s fundamental vocal melodies. Nevertheless, does that imply the piano within the intro, the background singers within the center part, and the electrical guitar earlier than “So that you assume you may stone me […]” aren’t a part of the melody?

One methodology for extracting “the melody” of a track is to think about essentially the most distinguished melody as essentially the most dominant one, sometimes recognized because the loudest melody within the combine. The chromagram is a broadly utilized illustration that visually shows essentially the most dominant musical notes all through a monitor. Under, you could find the chromagram of the reference monitor, initially with the whole instrumentation after which excluding drums and bass. On the left facet, essentially the most related notes for the melody (B, F#, G) are highlighted in blue.

Each chromagrams precisely depict the first melody notes, with the model of the monitor with out drums and bass offering a clearer visualization of the melody. Meta’s examine additionally revealed the identical remark, which led them to make the most of their supply separation software (DEMUCS) to take away any disturbing rhythmic parts from the monitor. This course of leads to a sufficiently consultant rendition of “the melody,” which might then be fed to the mannequin.

In abstract, we will now join the items to grasp the underlying course of when requesting MusicGen to carry out melody-conditioned era. Here’s a visible illustration of the workflow:

How MusicGen produces a melody-conditioned music output. Picture by writer.
Picture by Xavier von Erlach on Unsplash

Whereas MusicGen exhibits promising developments in melody-conditioning, you will need to acknowledge that the know-how remains to be a work-in-progress. Chromagrams, even when drums and bass are eliminated, provide an imperfect illustration of a monitor’s melody. One limitation is that chromagrams categorize all notes into the 12 western pitch lessons, that means they seize the transition between two pitch lessons however not the route (up or down) of the melody.

As an example, the melodic interval between shifting from C4 to G4 (an ideal fifth) differs considerably from shifting from C4 to G3 (an ideal fourth). Nevertheless, in a chromagram, each intervals would seem the identical. The difficulty worsens with octave jumps, because the chromagram would point out the melody stayed on the identical observe. Think about how a chromagram would misread the emotional octave leap carried out by Céline Dion in “My Coronary heart Will Go On” in the course of the line “wher-e-ver you’re” as a steady melodic motion. To reveal this, simply take a look at the chromagram for the refrain in A-ha’s “Tackle Me”, under. Does this replicate your concept of the track’s melody?

A chromagram of the refrain in “Tackle Me” (A-ha), bass and drums eliminated. Picture by writer.

One other problem is the inherent bias of the chromagram. It performs nicely in capturing the melody of some songs whereas utterly lacking the mark in others. This bias is systematic quite than random. Songs with dominant melodies, minimal interval jumps, and unison taking part in are higher represented by the chromagram in comparison with songs with advanced melodies unfold throughout a number of devices and that includes giant interval jumps.

Moreover, the constraints of the generative AI mannequin itself are value noting. The output audio nonetheless reveals noticeable variations from human-made music, and sustaining a constant model over a six-second interval stays a battle. Furthermore, MusicGen falls quick in faithfully capturing the extra intricate features of the textual content immediate, as evidenced by the examples offered earlier. It should require additional technological developments for melody-conditioned era to succeed in a stage the place it may be used not just for amusement and inspiration but in addition for producing end-user-friendly music.

Picture by Marc Sendra Martorell on Unsplash

How can we enhance the AI?

From my perspective, one of many main considerations that future analysis ought to tackle relating to melody-conditioned music era is the extraction and illustration of “the melody” from a monitor. Whereas the chromagram is a well-established and easy sign processing methodology, there are quite a few newer and experimental approaches that make the most of deep studying for this objective. It could be thrilling to witness firms like Meta drawing inspiration from these developments, lots of that are coated in a complete 72-page evaluation by Reddy et al. (2022).

Concerning the standard of the mannequin itself, each the audio high quality and the comprehension of textual content inputs will be enhanced by scaling up the dimensions of the mannequin and coaching information, in addition to the event of extra environment friendly algorithms for this particular job. In my view, the discharge of MusicLM in January 2023 resembles a “GPT-2 second.” We’re starting to witness the capabilities of those fashions, however vital enhancements are nonetheless wanted throughout numerous features. If this analogy holds true, we will anticipate the discharge of a music era mannequin akin to GPT-3 prior to we would count on.

How does this affect musicians?

As is commonly the case with generative music AI, considerations come up relating to the potential damaging affect on the work and livelihoods of music creators. I count on that sooner or later, it would turn out to be more and more difficult to earn a dwelling by creating variations of current melodies. That is significantly evident in situations similar to jingle manufacturing, the place firms can effortlessly generate quite a few variations of a attribute jingle melody at minimal price for brand spanking new advert campaigns or personalised commercials. Undoubtedly, this poses a menace to musicians who depend on such actions as a big supply of revenue. I reiterate my plea for creatives concerned in producing music valued for its goal musical qualities quite than subjective, human qualities (similar to inventory music or jingles) to discover different revenue sources to arrange for the long run.

On the optimistic facet, melody-conditioned music era presents an unimaginable software for enhancing human creativity. If somebody develops a charming and memorable melody, they will rapidly generate examples of the way it would possibly sound in numerous genres. This course of might help establish the best style and elegance to convey the music to life. Furthermore, it presents a chance to revisit previous tasks inside one’s music catalogue, exploring their potential when translated into totally different genres or kinds. Lastly, this know-how lowers the entry barrier for creatively inclined people with out formal musical coaching to enter the sphere. Anybody can now provide you with a melody, hum it right into a smartphone microphone, and share exceptional preparations of their concepts with mates, household, and even try to succeed in a wider viewers.

The query of whether or not AI music era is useful to our societies stays open for debate. Nevertheless, I firmly consider that melody-conditioned music era is without doubt one of the use instances of this know-how that genuinely enhances the work of each skilled and aspiring creatives. It provides worth by providing new avenues for exploration. I’m eagerly wanting ahead to witnessing additional developments on this subject within the close to future.

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