Transposition
The presence of the transposition function in the keyboard — switching the sound to a different key. When transposing, the pitch of all keys is simultaneously raised or lowered by a certain number of semitones. This function is useful in all cases when a melody learned in one key needs to be played in a different key — for example, if the original melody is too high or too low for the vocalist, if the external accompaniment differs in key, if you need to switch between keys during the song, and etc. In such situations, by transposing the sound, you can play a melody in a new key using the same familiar keys without relearning it.
Transport control
The presence in the keyboard of
the transport control function.
In this case, we are usually talking about support for the MIDI Machine Control standard, designed to control external recording and playback equipment. Such support actually turns the keyboard into an external remote control, allowing you to give commands from it to "Play", "Stop", "Pause", "Rewind" (forward and backward) and "Record". To do this, the design provides a separate panel with a set of appropriate buttons.
MIDI out
A specialized output for transmitting MIDI signals to an external device — a sequencer, a computer sound card (if there is a MIDI In input), etc.
MIDI signals are a kind of "digital notation": they tell which key was pressed, with what force and for how long, and also carry information about various additional parameters: timbre, tempo, key, etc. To convert such signals a "ready" sound requires an external sequencer (software or hardware).
Note that despite its specialized purpose, the
MIDI Out output is not mandatory for modern MIDI keyboards: MIDI signals can also be transmitted via other interfaces, such as USB or Bluetooth (see the relevant paragraphs). So it makes sense to specifically look for a keyboard with such a connector if you plan to connect it to equipment with a MIDI In input.
Tablet stand
Holder for a tablet computer or smartphone in the design of a MIDI keyboard. Usually, this is a device on which the gadget is installed almost vertically (with a slight tilt back).
The stand replaces the music stand for the music displayed on the screen of mobile devices, and it also provides a comfortable placement for a connected tablet or smartphone.
Display
The type
of display that the keyboard is equipped with.
Most modern MIDI keyboards have relatively simple monochrome (single colour) displays. Such screens are inexpensive, and their capabilities are sufficient for most cases. However, there are also models with colour screens — usually, such equipment is a sign of an advanced keyboard with an abundance of additional functions; for simpler devices, a colour display is overkill.
