Novelty is an aesthetic value. In Classical aesthetics, it was seen as a negative, because novelty represented divergence from a universal artistic "ideal." Romantic aesthetics embraced novelty as a value as a by-product of other, more important artistic values like creativity. The difference between novelty and creativity as aesthetic values is grounded on the reception of a specific work by the Audience for that work. Novelty is the perception by the Audience that the work is "new" or "different" than the art products they are presently consuming. This perception may itself be "false" in that something that is perceived as novel can be completely unoriginal/creative in that it can be utterly derivative of some work that has come before.
This distinction is important one for career Artists to grasp, whatever field they may inhabit. Artists are often obsessed with creativity and look down on novelty (if they even have an opinion on the subject of desirable aesthetic values.) But, in fact and in truth, creativity is essentially unimportant while maintaining novelty is perhaps THE crucial value for survival in the market for cultural products among the general population. In the context of popular music, novelty can be introduced into a body of work by a variety of different methods.
The most standard strategy is to incorporate new influences into an existing sound or style of music. This is a simple, obvious, well established, productive way for Artists to prolong their careers in the market for cultural product, but it can be more or less succesful, or not succesful at all. The cliche is of a mid-career shift in sound and style that calls into question the prior work, such as when a dance rock artist becomes a freak folk artist (Edward Sharpe and the Magnetic Zeroes.) At the other end of the spectrum is an Artist like Nick Cave or Tom Waits, who incorporate new styles in every production cycle so that each product is unexpected. In the center you have the world of Top 40 where stylistic flourishes and improvements in production technology create a kind of Mannerist sensibility that carefully redesigns the recent past with an eye for the present.
This places the burden for introducing that novelty on the artist themselves. Here are some suggestions that I have for musical/stylistic influences:
1. West African Banjo/Gnawa music: One of the most important elements of popular music is rhythm. In the associated worlds of rock and country music, a common element is the "rhythm guitar." Much Top 40 country music uses an analog: rhythm banjo, which often exists immediately alongside an accompanying guitar, or multiple guitars. Personally, I don't think swiping a country banjo and putting it in a rock/indie tune is a very cool idea, but finding a banjo substitute, which is exactly what you get in Gnawa music. The Banjo is FROM West Africa, so of course, their music is authentic/good/interesting etc.
2. The Classic Age of Berlin Techno: It is clear that there is a vast, overlapping critical/popular Audience for electronic dance music. Whether it be the genre classification for Album Reviews at Pitchfork, or an EDM Artist selling out the Hollywood Bowl in less than an hour, Electronic music is alive on a number of fronts. At the same time, there literally exists DECADES of electronic music that was indie/fringe/not absorbed by the larger general market, even music of the 90s, like Chemical Brothers or The Prodigy are examples of music that would be perceived as "novel" by an overlapping critical/general Audience- potentially- who knows right? But along with "big beat" there is a wealth of Berlin Techno that is magnetic and probably easy enough to reproduce with existing technology- a music that would be both futuristic and nostalgic at the same time.
3. The Cinema of Eastern Europe During the Cold War: Whether it be Czech New Wave, Russian Cinema, Polish Cinema, the films of Eastern Europe/Russia are "cool" and very under appreciated. It is easy to see a vogue for them being established in the same way that the French New Wave is periodically revived by contemporary artists. This is something that could be reference simply by something as simple as a song title or even through artist social media.
4. The Cultural Overlap between the Jazz Age in NYC and surrealism in Europe and the US: Although the beginnings of surrealism stretch back into the 19th and even 18th century, the surrealist "movement" "began in the early 1920s." (Wikipedia) Although neither the surrealist program NOR the jazz age are particularly viable on their own, or rather, they are already incorporated into the taste of a general or critical audience and thus valueless in terms of novelty, there is potential to combine the two things into an influence that might play well.