Building a voltage adjuster circuit
I'm using uA741 op amps.

There's your problem then.  That thing was obsolete in the 1980's.  The data sheet that I have for an LM741 lists an output voltage swing of \$\pm16\mathrm{V}\$ with input power rails of \$\pm20\mathrm{V}\$ -- and that's with a \$10\mathrm{k}\Omega\$ load resistor, so about a 15mA load current.  That means you need four volts of overhead just to drive 15mA out of the thing.
To do this with less supply voltage, you need a rail to rail op-amp, or you need a much bigger voltage supply -- if you carry on with the 741 theme, you'll need -5V and +10V supplies.  If you do carry on with the 741 theme, your next question will be &quot;why does my audio sound so crappy?&quot; because the 741 is not a good audio op-amp.
I would recommend that you scour the web for a guitar preamp circuit.  Take the output of that, and capacitively couple it to a voltage divider that rides at 2.5V.  Then either run that straight into your ADC, or buffer it with a unity-gain stage and run that into your ADC.