Normally the bars of a song are numbered from 1 through to the number of bars in the song, and playback begins at bar 1.

However, Songtrix offers the option, in the song setup, of adding one or two pickup bars to the beginning of the song.  Pickup bars are numbered with the roman numerals i and ii.

Sometimes a melody has a few "prefix" notes leading in to the actual starting bar of a section.  The purpose of the pickup bars is to provide a place for these notes, without disturbing the overall structure of the song.

There are many songs which work like this, a good example is When The Saints Go Marching In, as shown below.

As you can see, it has three leading notes for "Oh when the", but the real action of the song doesn't start until "saints" in bar 1.

When a pickup section exists in a song, the section label (pickup) is displayed, unless you define an alternative marker label for the first bar.

There is an important feature of the pickup section with loop playback, where it is played only at the start of the first loop.

For repeat loops, playback restarts at bar 1, and the pickup section is either ignored or merged with the last bar(s) of the previous loop, depending on the song's Loop Pickup setting.