If you want to tinker with a small PA that doesn't break the bank, then you can't go much wronger than a Hohner Student. They come with a wide variety of bass layouts, some more useful than others. But (in the UK at least) you can often pick up decent working ones. They tend to have 25 or 26 keys. The lightest have 12 bass - a row of bass (BbFCGDA) and major chords. It is possible to mute the major chord thirds with tape to make them more useful. There are also 24 bass versions, with 8 bass, maj/minor chords, though they annoyingly run AbEbBbFCGDA, when you often don't really want ..at least...the Ab and have an E instead on the other end. The Hohner Verdi I is slightly bigger, with 34 treble keys and 48 bass. The bass has all 12 notes, maj/min/fundamental and counter bass row.The problem with the Verdi I is that they are all old so getting a good *working* one is harder. Restored I think they sound great, esp compared to the modern Chinese made accordions. And they are v light indeed.