Or, if really enamored by analog cassette mystique, record the show with far less hassle to a digital recorder, then once home, dub the output from it to cassette. Instant hipster retro!
Extra credit for recording the cassette output back to the same digital recorder again, transferring both files to the computer, aligning, playing back both mixed together with polarity flipped on one of them and level adjusted so as to achieve as deep a cancellation between the two as possible.. and grooving out to the difference signal, which will be the distilled essence of what the cassette tape is doing to the sound.