[quote name='Matty' post='954239' date='Sep 12 2010, 11:57 PM']how about a boss LS-2.
volume control over both basses, simple stompbox format, dead cheap.[/quote]
[quote name='thisnameistaken' post='954256' date='Sep 13 2010, 01:08 AM']I'm surprised it took this long for anyone to mention the swiss army LS-2.
You can pick them up used for about £40 usually, they are useful for tonnes of stuff, anywhere you can imagine needing an A/B loop/switch or a simple 2-channel mixer.[/quote]
+1 to all of this. I will be using an LS-2 I recently purchased in this exact fashion.
1. Plug loud bass into input, output to rest of pedals/amp.
2. Plug quieter bass into return A.
3. Set mode knob to A<->Bypass, so the pedal switches between bypass (loud 5 string) and Loop A (quiet fretless) going to the amp.
4. Set the level of your quiet fretless using the volume knob for channel A until equal with the 5 string.
5. When you switch basses hit the LS-2 and away you go!