The HTC myTouch 4G Slide is an Android smartphone that is sold exclusively through T-Mobile. In fact, the phone is branded as T-Mobile as the manufacturer, not HTC, although HTC does in face make the phone for T-Mobile. It mainly features 4G data speeds (but, surprisingly, not 4G LTE), and it offers a slide-out physical keyboard, which is the main reason I bought it. I mainly use my cell phone for taking notes, and it's especially useful for writing down song ideas and lyric ideas on the go. That is why a physical keyboard was so important to me, and there are fewer and fewer smartphones with physical slide out keyboards…the trend seems to be moving towards compactness, less buttons, and larger touch screens.
The physical keyboard on the myTouch 4G Slide is descent, but it doesn't seem as well engineered as the original Droid line (which all have slide out keyboards, up through Droid 4). Also, there isn't a dedicated keyboard line for numbers, and that makes it pretty difficult and time consuming to write any sort of number info on your phone. The alt key needs to be continually pressed, which can be annoying. The Droid 4 made room for dedicated number keys, but not here.
Android phones in general, in my experience, are okay with musical apps, but not nearly as useful as apps on the iPhone or iPad lines. Simple metronomes can be hard to make without skipping, although I finally found one that does work well (among the dozens that are pretty inaccurate and wobbly). Microphone tuning works pretty well too. But playing actual instruments, drums, or samples though the touchscreen or any other input is a joke; there is just too much lag and latency to make it work. This is very unlike piano apps on Apple devices, which work flawlessly, and are very enjoyable to play.