The two most fundamental events in Midi are the Note On and Note Off events.  These are the events that are sent from a piano keyboard when a key is pressed and then released.

These events have three important properties attached to them.

Note Pitch

The pitch of a note is how low or high it sounds.  You can easily imagine this in terms of the keys on a piano keyboard, going from left to right.

Midi assigns each pitch (or key) a numeric value from 0 to 127 (most Midi values also use this range, with the exception of channels, explained below).

Since there are twelve pitches in an octave, this allows Midi to reference about ten and a half octaves, which is adequate for just about any imaginable musical composition.  Middle C is given the the value of 60 in this range.

Songtrix always refers to notes by pitch name, so you won't need to be concerned about these numbers.  Pitch names can range from C0 to G10 (where Middle C=C5).

Note Velocity

The velocity of a note is how strongly it is played.  For a piano keyboard, this means how hard the key is pressed.

As you might imagine, a higher velocity produces a louder note, but (depending on the sophistication of the synthesizer) it can also change the tone.  For example a trumpet voice at low velocity might sound subdued and mellow, but at high velocity more bright and brassy, just like a real instrument.

Velocity is independent of either the track level (which applies to all the notes in a track) or the master volume (which applies to all notes in a song).  They all combine to produce the ultimate loudness of the played note.

Velocity can be different for each note and is a major factor in the realism of Midi music.  A series of notes with the same velocity can sound mechanical and dull, whereas human expression almost always involves a range of velocities.

Songtrix maintains a velocity property for most events.  Like most Midi values, it is in the range 0 to 127, but at your preference it can be expressed as a percentage.

It also has a range of functions to adjust the velocities of a group of notes, including humanizing them (adding a random variation to make them sound more realistic).

Midi Channel

The Midi protocol started as a way for a piano keyboard to transmit one part of a song to a sound module.  However, the designers had enough foresight to build in the capacity for sixteen independent Midi channels.

Thus a single Midi sound module can play a complete song arrangement of up to 16 parts at once, including perhaps a piano, guitar, trumpet, bass, drums, and whatever else.

With very few exceptions, Midi note and controller events are targeted to a specific channel, leaving the other channels unaffected.

In Midi itself, the channels are numbered from 0 to 15.  But for the comfort of people who are not familiar with the zero-based counting of computers, these are often renumbered for display purposes as channel 1 to 16, simply by adding 1.  Songtrix offers a choice.

Midi channel 9 (ch.10 for 1-based numbering) often has the special status of being of the percussion channel.  Instead of the notes playing the same voice at different pitches, they each are configured to play a different drum sound from a drum kit.