Both, and just about anything else.
Its a relative pitch training program.
There's two types of pitch recognition that you can obtain/born with.
The 1st is perfect pitch. Its fairly rare, and its something that is generally picked up at a very young age, or perhaps even prenatal. Its where people can tell the pitch of anything they hear. Like someone might fart, ande they'll go "nice fart, it was a C#"
The other is relative pitch. Having exceptional relative pitch is practically a prerequisite to becoming a HEAVY player. Relative Pitch is where you know what a certain pitch is, due to its relation to the initial pitch that was played(i.e. interval recognition). Its basically just being able to memorise what certain intervals, and chord movements sound like. So intern, you should be able to transcribe things MUCH faster, and with the use of relative pitch, you should be able to construct melodic lines in your head and then simultaneously apply them to bass. Also when composing, it aids in being able hear and sing melodys and chordal movements before you actually twiddle with your instrument or put pen to paper
Its not something that just
happens though.....its fargin hard, and it can be fargin boring, but its something that should be worked on if you wish to progress 'that' level of musicianship, or if you a have desire to "seriously" play jazz, or other demanding genres.
This prog is just a good little training tool that helps you work on it in your own time. If you do happen to check it out, make sure you can sing the stuff aswell aswell as hear it. You may sound
funny singing to yourself, but meh, its all good

Btw, i suck at it