A few weeks ago I was forced to listen to a recording of Bryn Terfel covering What a Wonderful World, the song made famous by a hoarse-voiced Louis Armstrong. I say ‘forced’ because my inner snob wouldn’t have touched the recording with somebody else’s barge pole. Work commitments, though, made it unavoidable.

Terfel’s new album 'Homeward Bound' – a selection of pop covers, sacred songs and hymns performed with the Mormon Tabernacle Choir – lives up fully to the schmaltz of its title. I’d be lying if I said it was my cup of tea, or that I ever want to hear it again. But I’d also be lying if I said Terfel’s What a Wonderful World didn’t bring a broad smile to my face and a tear to my eye.

It was partly the charming simplicity of that song and its almost-tasteful scoring. But it was mainly the wonder of Terfel’s voice and its way with words, music and meaning. When I met him shortly after listening to that song, he told me that he’s looking to record Die Winterreise. So impressive is Terfel’s caressing of every word of What a Wonderful World – every vowel-sound, every meaning, every mood – so un-contrived is his placing of its consonants – that I immediately linked the little ditty to one of Schubert’s. It opened-up the serious potential of Terfel’s Winterreise plan.

That inner snob presumed – rightly or wrongly (probably wrongly, but only because of compelling historical evidence) – that an opera singer covering a pop song would result in a tasteless sonic car crash. Here are two specialist aesthetics which rarely combine for the greater good, and which you might well argue should respect one another by never combining at all. Terfel, though, rose above those semantics and brought his honest (dare I say transcendent) musicality to bear. In What a Wonderful World, he elevates the songwriters (Bob Thiele and George David Weiss) but he elevates himself and his remarkable instrument, too.

Experiments like these – cover versions, musical re-clothings, artist tributes – fail when one or more of the assets involved is debased rather than elevated. It takes quite a lot for me to not be rendered agog with wonder by Bach’s Passacaglia and Fugue in C minor – my vote for the cornerstone of musical civilisation – but Leopold Stokowski’s romanticised re-upholstering of the organ piece for large orchestra makes my skin crawl. Stokowski had his reasons for making the transcription in 1922, but in 2013 it has to be recognised as one of the most tasteless, garish, ill-attuned and point-missing musical endeavours of all time.

I made the connection because a new recording of Stokowski’s arrangement of the Passacaglia arrived in the same Deutsche Grammophon parcel as Byrn Terfel’s 'Homeward Bound'. Full marks to conductor Yannick Nézet-Séguin for tapping into his Philadelphia Orchestra’s heritage and saluting its former conductor with such an interesting album. Now let’s recognise that Stokowski’s ‘transcriptions’ of Bach belong in the same musical bracket as Vanessa Mae’s electric violin arrangements: that marked ‘plain wrong’.

Without Stokowski – his pioneering and visionary approach to sound recording (funnily enough he recorded with the Mormon Tabernacle Choir as well as the Philadelphia Orchestra) and his laudable ideas about what audiences respond to – the music world would be much the poorer (and not just ‘classical’). But he sees in Bach so much that simply isn’t there: sheen, mist, gloss, tidal push-and-pull, luminous colour and overt Hollywood-style entertainment.

An outstanding organist could play the Passacaglia and Fugue on one organ registration and still unlock its most beautiful truths: a simple-yet-complex harmonic journey realised through breathtaking counterpoint. Stokowski debases Bach’s whole endeavour with booming timpani thwacks, warmed-up brass, slithering woodwinds and a luscious ocean of strings (Nézet-Séguin fascinatingly re-creates the ‘free bowing’ style Stokowski developed in Philadelphia, and yes, it sounds horrid and sickly). In going big on musical line and bass-thrust, Stokowski belittles all those delicious single notes, clockwork arpeggios and felicitously-placed chords that make the Passacaglia and Fugue so enduringly delicious. All it needs is some coloured lights projected above the stage. Ah…it turns out that in Philadelphia, Stokowski did that, too.

I’ll happily salute the musical dynamo that was Leopold Stokowski by wallowing in one of his sumptuous Tchaikovsky or Wagner recordings – music that should be romanticised because it’s, well, Romantic. But give me Bryn Terfel covering a pop song over Stokowski covering Bach any day. At least Terfel knows how to respect and elevate a work’s existing musical qualities, rather than inventing his own entirely unrelated ones.