I uh... made a sound cannon... because reasons...
So this is another RWBY-inspired weapon design. Unlike most of my other weapon concepts, which actually mostly make sense as weapons on their own to some degree, this one is designed to function in tandem with the user's semblance, like a mage-type weapon, except this person doesn't use glyphs.
Semblance: The user's semblance is the ability to manipulate pressure waves, altering their direction and amplitude. However he can only manipulate the waves shortly after they are created, making the degree to which he can modify them fairly limited, and it requires him to have good timing. If his reactions are too slow, then he loses his short window that he can manipulate the wave, however the uses are still fairly varied when used properly. For example, he could manipulate an impact such as a normal punch, and make it feel like it was coming from a heavy-weight boxer. Or if an explosion goes off nearby, if he's fast enough he could lessen the pressure from the blast in his direction to make it survivable. But like I said, manipulating waves he didn't create is harder as it requires extremely good timing and reaction speed. Along with the semblance, the user also has a form of synesthesia called Chromesthesia: the association of sounds with colors. Basically he can 'see' music, which aids him in his ability to manipulate and aim sound.
Well now you probably were able to tell where this is going. Sound is simply a series of pressure waves, and using music as a weapon means that if he already knows the song, then he can have perfect timing to manipulate the blast. He has pre-arranged music at his disposal, as well as a synthesizer to generate music on the fly as needed, as different tones have different effects when amplified. For example the higher tones are like thin, sharp bullets; piercing through flesh easily, while the bassier tones are more like forceful impacts, but are able to more easily affect a larger area. As such the lower tones are better for knocking multiple enemies back, breaking armor, and destroying obstacles, while higher tones are better for more accurate, longer-ranged killing blows.
And of course it transforms into a hammer as well ~so that he can drop the bass~ In this mode he focuses more on using the sound to propel the hammer, allowing for much faster swings, and in turn larger impacts, which can be amplified exponentially larger as well. As such this allows for moves like crater-slams, or a 'golf swing' that can send opponents flying.
Oh, and of course there's an overkill mode, because you can't have enough speakers.
One of the main advantages of this weapon is that it doesn't really take ammo, as it only needs electricity to function, a single charge lasting far longer than should be needed for even multiple battles. And even if a charge is needed, some yellow dust can easily refill the battery. However it does require near-constant use of the user's semblance in order to be effective, which can be straining over time. If a battle goes on for too long, he can easily start to tire out and have his attacks lose their effectiveness until he has time to rest and recharge. Not to mention that distractions and the like can ruin an attack if he loses focus.