I did this for years and some fairly general points.

As you are using BIAB you are probably generating songs in advance so you need some way of choosing and playing back on demand.

I have only just upgraded to BIAB 2018 from 2008 so all our stuff used to be midi only. It was easier to create in BIAB and edit in PowerTracks. We used a yamaha file player and a roland sc7 sound module fed straight into the PA. Both probably available on ebay or you could use a laptop with a soft synth like the edirol hypercanvas installed and play from PT or BIAB with the sound from the headphone socket going to the PA. BIAB - unless you freeze tracks generates the song every time you play it so if you want the same arrangement every time we found midi files created in BIAB then transferred to PT was the best way to go.

That was in the days of midi but these days BIAB sounds great with RealTracks that mean your sound is audio not midi. Save the BIAB track to an mp3 format and you can play it live. If you have a laptop save all the files to a single directory and then play with the default music player - again with a lead from the headphone socket to the PA. It's easy to select songs (the files will be in alphabetical order) and you have a modicum of volume control on the laptop (assuming it's close to the mic stand) without turning round to the PA. Obviously the same applies if you are using a mixer.

A much smaller 'rig' is an Ipod touch connected the same way. Trouble is when you play one mp3 the next file starts automatically which is a pain playing live. I asked the forum and the best way to solve that problem is 'one set list per song' which is a faff to set up but works fine on stage. Even the oldest Ipod touch will do and it's better to have a dedicated Ipod than the one you use every day. Ebay has used ones cheap.

I played in a duo so we could harmonise but solo, technology can help you. If you are a guitarist you plug your guitar and mic cables into a Harmony Singer 2 pedal which then has outputs for the mic and guitar signals. The pedal listens to the guitar chords and adds a suitable harmony to your voice.

Of course if you are using mp3s then you can record the harmony part in BIAB, RB or PT and sing along live with your own voice behind you. And don't forget BIAB now has oohs and aahs you can use as backing.

Hope that helps