Prior to its acquisition by Apple, the Beats sound was very easily expressed as being bass-heavy, and while that's a simplification of the kind of equalisation that Beats applies to its headphones, it was definitely its signature tone.
In more recent Beats offerings, such as the Powerbeats Pro, the company has tended towards more general equalisation, although it stresses that it tries to master break out vocals and instruments in its own equalisation. There's no choice of equalisation modes for the Beats Solo Pro headphones, but it's certainly not what I'd call aggressively bass-heavy in the way that classic Beats headphones have been. I'm a fan of that approach, but of course, if you prefer more doof in your music, you might find it annoying.

The slow deliberate guitar and drum opening of Prince's Purple Rain echoed nicely in the Beats Solo Pro's cans, while the voice track was nicely differentiated, something that's often muddied in more bass-heavy headphones.
Switching to the more bass-heavy line of Ice Cube's Hello, a track that should work well with the Beats Solo Pro given the presence of Dr Dre, I still felt the underlying bass lines coming through heavy but clean.

Quieter and more deliberate tracks such as David Bowie's Life on Mars? presented well with good high tones mixed in with the raising orchestra as the song progresses.
The raw throaty performance of Peggy Lee's Fever stood out well against the simple bass and drum line on that track, and the sheer pop cheese of Britney Spears' Work Bitch showed just how heavily produced that track really is. Freddie Mercury's gradually increasing vocals on Barcelona contrasted nicely with Montserrat Caballé's soaring operatic tones. I could go on, but I think you get the point.
Given the experience I had with the Powerbeats Pro, I'd expect solid audio quality, really, and for on-ear headphones they're really very good in this aspect.
The other big selling point for the Beats Solo Pro is that they're the company's first headphones with active noise cancelling built in. Active noise cancelling works by using the external microphones to analyse the external audio environment to create, in effect, an equal but opposite noise cancelling wave. The Beats Solo Pro headphones use Apple's own H1 chip for processing, and it's admittedly a difficult matter for on-ear, as distinct from over-the-ear, headphones to manage.

It's a trick that the Beats Solo Pro headphones manage well, but not to a level where I'd call them best in class. Part of that is undoubtedly the loss of noise isolation that you'd get with full over-the-ear headphones, but it's also because there's no option to level out the noise cancellation on the Beats Solo Pro. It's either on or it's off, and the strength of its effect wasn't always enough to provide me with the level of isolation I'd really like. Certainly wearing them and testing them side by side with the Sony WH-1000XM3 headphones, I was left in no doubt as to which was the superior pair for noise cancelling.
Spoiler: It wasn't the Beats Solo Pro, but if you're a fan of the on-ear approach they're about as good as you're likely to get.
The Beats Solo Pro will work wirelessly with Apple's own Siri if you're pairing them to an iOS device, and they notably don't have any kind of on/off switch to engage with your chosen smartphone. Like competing designs, they instead power up when you unfold them, which is nice engineering, if not actually unique.

However, one trick I wish Apple had borrowed from other designs is pausing when you're not wearing them. It's totally binary; if you fold them up they power down, but there are plenty of pairs that also pause music playback if you take them off or wear them around your neck. Now, Beats' position on this is that this is what transparency mode is for, so you can hear the outside world easily. Transparency mode is where the external microphones switch outwards to pick up more of the real world at the tap of a button.
The dedicated button on the Beats Solo Pro is a much better solution than the annoying tapping you have to do on the Apple AirPods Pro, but I still can't help finding the whole thing rather creepy whenever I engage it as a mode. Is it just me that would rather remove headphones if I'm talking to somebody? Does nobody else feel like they're eavesdropping by using this mode?
I primarily used the Beats Solo Pro paired with an Apple iPhone 11 Pro Max, and not surprisingly, it's an experience that's optimised for iOS users. Unfolding and pairing on an iOS device will grant you an animated view of your headphones in the accurate colour tone as well as a rundown of current battery life, something you won't get when pairing with an Android phone.